EJIKEIEY 

I.1BRARY 
lij-'iivtRsiTY  or 

CAIIPORNU 


DONATED  TO  AOA  LIBRARY  BY: 

Dr.  Gordon  C.  Shlvas 
Madison  Street 
Pulaski,  Tennessee 


propertKof  mmm 

7000  C\m^^^  5^''^^^"^ 


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^ 


SUPPLEMENT    TO 
THE 

OPTICIAN'S  Manual 


Copyright,  1S99,  by  B.  Thorpe 
Publisher  of  The  Keystone 


SUPPLEMENT  TO 

THE 

OPTICIAN'S  Manual 

CHAPTKRS  11  AND  12. 


A  Treatise  on  the  Science  and  Practice  of  Optics, 

COMPII^KO    FROM    TIIH    SKKIAI,    WRITTEN'    HY 

C:  H^Brown,  m.  d., 

Graduate  I  'nivetsily  of  Pennsylvania  ;  Piojessot  of  Optics  and  Refraction  :  formerly  Physician  of 

the  Philadelphia  Hospital;  Member  Philadelphia  County,  Pennsylvania  State 

and  American  Medical  Societies. 


Published  Exclusively  in  Tin.   Kkvstonk,  the  Organ  of  the  Jewelry 
and  ()j)tical   Trades. 


WITH   ILLlJSTRATIOiNS. 


PrBI-ISlIKO    BY 

THK  KKVSTONE. 

19TH  AND  Brown  Strkkts,  Phil.\dei,phi.\,  Pa.,  T. S.  A. 

1899. 


^r 


0?XO\-Z,K 


OPrO 


f'rkface:. 


T^HIS  Supplement  to  "The  Optician's  Manual"  has  been 
*-  compiled  in  response  to  repeated  and  ury^ent  requests  that 
we  republish  in  book  form  the  two  chapters  of  TiiK  Kkvstone 
serial  which  covered  the  important  subjects  of  Hypermctropia 
and  Myopia.  These  two  chapters  are  a  direct  continuation  of 
the  matter  published  in  the  Manual,  and  all  who  have  read  them 
concede  that  there  is  no  book  available  to  the  optician  in  which 
Hypermctropia  and  Myopia  have  been  treated  so  clearly  and 
exhaustively.  As  in  the  case  of  "The  Optician's  Manual,"  the 
matter  is  written  in  such  a  way  as  to  be  readily  intelligible  to 
the  beginner,  while  containing  all  the  information  needed  by  the 
experienced  optician.  In  presenting  this  Supplement,  we  are 
happy  in  having  the  endorsement  beforehand  of  the  profession  at 
large,  including  optical  teachers,  students  and  practitioners. 


ozrz 


COXTKX' 


Chapter  11. 

HYPERMETROPIA 11 

History  of  Hypermetropia.  Characteristics  of  Hyperme- 
tropia.  Hypermetropia  Hereditary.  Divisions  of  Hyper- 
metropia. Theory  of  the  Correction  of  Hypermetropia. 
Accommodation  of  Hypermetropia.  Latent  Hyperme- 
tropia. The  Ophthalmoscope  and  Hypermetropia.  Vis- 
ion and  Hypermetropia.  Estimation  of  the  Total  Hyper- 
metropia. Latent  vs.  Manifest  Hypermetropia.  Hyper- 
metropia in  Children.  Testing  Hypermetropia.  Metliod 
by  Over-correction.  Spasms  of  Accommodation.  What 
Glasses  to  Prescribe.  Why  Glasses  Should  be  Worn. 
Rules  for  Determining  the  Glasses.  Proper  Fit  of  Glasses. 
Sequalec  Hypermetropia.  Hypermetropia  and  its  Rela- 
tion to  Neuralgia,  Spasms  of  Accommodation,  Blepharitis, 
Styes,  etc.,  Glaucoma,  Cataract,  Myopia,  Asthenopia, 
Strabismus,  Retinitis,  Neuritis  and  Nervous  Derangements.  S  / 

Chapter  12. 

MYOPIA 114 

Forms  of  Myopia,  Causes  of  Myopia,  School  Statistics, 
Why  Children  are  more  prone  to  Myopia,  Myopia  Heredi- 
tary, Preventive  Measures,  Vision  of  Myopes,  Determina- 
tion of  the  Existence  of  Myopia,  Diagnosis  of  Myopia, 
Myopia  and  Amblyopia,  Can  Myopia  be  Cured  ?  Does 
Age  Improve  the  Myopic  Eye?  Second  Sight,  Progressive 
Myopia,  .Apparent  or  Accommodative  Myopia,  Symptoms 
of  Myopia,  Prevention  of  Myopia,  Tests  for  Myopia, 
Treatment  of  Myopia,  Prescribing  Glasses  for  Myopia, 
How  Myopia  Disturbs  the  Normal  Relation  Existing 
between  Accommodation  and  Convergence,  Treatment  of 
the  Muscular  Insufficiency  accompanying  Myopia,  Muscle 
Tests,  Surgical  Treatment  of  Myopia,  Myopia  in  Relation 
to  Eye  Strain. 


CHAPTER  XL 


IIVPERMETROPIA. 


Having  given  a  careful  representation  of  the  anatomy  of 
the  eye  and  the  physiology  of  vision,  as  well  as  of  the  simpler 
laws  of  optics  and  the  properties  and  uses  of  lenses,  and  having 
enumerated  the  outfit  required  and  given  minute  directions  as 
to  the  method  of  examination  of  a  case  of  supposed  optical 
defect,  together  with  a  detailed  description  of  the  loss  of  ac- 
commodation and  the  diagnosis  and  treatment  of  presbyopia 
and  its  complications,  we  pass  on  to  the  consideration  of  the 
various  optical  defects.  Tlie  first  one  to  be  studied  will  be 
hypeniwtropia,  as  being  perhaps  the  error  of  refraction  with 
which  the  optician  meets  most  frequently. 

The  word  hypermetropia  is  made  up  of  three  Greek 
words,  signifying  in  excess  of  the  lueasitre  of  the  eye.  It  may 
be  defined  as  that  condition  of  the  eye-ball,  in  which  the 
antero-posterior  (from  in  front  backward)  axis  of  the  ball  is 
too  short;  in  other  words,  the  globe  of  the  eye  is  too  flat,  which 
is  equivalent  to  its  refracting  power  being  insufficient,  so  that 
parallel  rays  of  light  entering  the  eye  cannot  be  brought  to  a 
focus  upon  the  retina  when  the  accommodation  is  at  rest,  as 
it  should  be  when  we  are  looking  at  distant  objects. 

HISTORY  OF  lIVPERMKTROriA. 

Although  hypermetropia  had  been  mentioned  and  de- 
scribed bv  previous  writers  somewhat  indefinitely,  it  was  re- 
served for  Bonders  to  reduce  the  knowledge  concerning  it  to 


12  HYPERMETROI'lA. 

scientific  accuracy;  but  it  was  not  until  1848  (less  than  half  a 
century  ago)  that  he  published  his  first  description  of  this 
defect,  and  cleared  the  optical  atmosphere  surrounding  it, 
which  had  pcrviously  been  cloudy  and  misty  with  speculation 
and  error. 

The  elucidation  of  this  hitherto  mysterious  defect  was 
the  magnificent  result  of  many  years  of  patient  toil  and  sys- 
tematic investigation  of  the  subject,  in  the  light  of  the  knowl- 
edge concerning  it  which  was  at  that  time  the  property  of  the 
scientific  men  of  the  day,  together  with  the  added  fruit  of 
Bonders'  own  research  and  discovery,  just  as  many  other  great 
truths  have  been  evolved  by  a  similarly  slow  process  but  by 
a  persistent  application,  such  as  has  characterized  the  labors 
of  many  of  the  great  minds  of  the  age. 

Previous  to  this  time  many  affections  of  the  eye  were 
misunderstood,  because  of  the  imperfect  knowledge  of  these 
matters  available  at  that  day,  and  were  supposed  to  have  their 
origin  in  the  nervous  system  of  the  eye.  In  the  light  of  our 
present  knowledge,  however,  many  of  these  cases  were  hyper- 
metropic, and  the  distressing  symptoms  were  caused  by  the 
strain  imposed  upon  the  accommodation  in  its  unaided  efforts 
to  overcome  the  defect. 

DONDERS'  OWN  W^ORDS. 

"He  who  knows  by  experience  how  commonly  hyper- 
metropia  occurs,  how  necessary  a  knowledge  of  it  is  to  the 
correct  diagnosis  of  the  various  defects  of  the  eye,  and  how 
deeply  it  affects  the  whole  treatment  of  the  oculist,  will  come 
to  the  sad  conviction  that  an  incredible  number  of  patients 
have  been  tormented  with  all  sorts  of  remedies,  and  have  been 
given  over  to  painful  anxiety,  who  would  have  found  im- 
mediate relief  and  deliverance  in  suitable  spectacles. 

"It  is  a  great  satisfaction  to  be  able  to  say  that  asthenopia 
need  now  no  longer  be  an  inconvenience  to  any  one.  In  this 
w-e  have  an  example,  by  what  trifling  means  science  sometimes 
obtains  a  triumph,  blessing  thousands  in  its  results.  The  dis- 
covery of  the  simple  fact  that  asthenopia  is  dependent  on  the 
hypermetropic  structure  of  the  eye,  pointed  out  the  way  in 
which  it  was  to  be  obviated." 


HYPERMETROPIA, 


13 


PROF.   BONDERS 

Is  one  of  the  best-known  men  conneced  with  the  ophthal- 
mology of  the  preceding-  generation,  and  his  name  is  a 
familiar  one  to  every  optical  student  of  the  present  day.  His 
death  was  an  irreparable  loss  to  ophthalmology  and  to  optics, 
w^hich  is  shared  and  felt  by  every  individual  practitioner  and 
worker  in  this  field.  But  it  has  been  truthfully  said  by  one 
of  his  biographers  that  "we  do  not  lose  the  master,  since  his 
works  remain  and  will  always  remain,  forming  the  life,  the  soul 
of  ophthalmology." 


.   /^ 


I'HOV.   DONUEI 


Donders  pursued  a  medical  course,  and  at  the  early  age 
of  twenty-two  years  occupied  a  teacher's  chair,  followed  two 
years  later  by  his  elevation  to  the  professorship  of  anatomy  and 
physiology  in  the  University  of  Utrecht,  from  which  he  had 
so  recently  graduated,  and  in  which  he  continued  during  all 
of  his  active  professional  life,  building  up  an  international 
reputation  that  was  limited  only  by  the  size  of  the  world,  and 
making  of  this  little  city  of  Utrecht  a  scientific  center  that 
emitted  its  radiance  in  every  direction,  and  attracted  the  at- 
tention of  learned  men  of  every  clime.  Donders  was  indeed 
a  foremost  representative  of  Holland  in  the  noble  galaxy  of 
savants  that  were  cultivating  the  fertile  fields  of  science. 

Donders  did  not  confine  his  researches  to  any  one  portion 
of  the  field,  but  his  labors  extended  over  the  whole  domain  of 


14  HYPERMETROriA. 

science,  in  which  are  found  everywhere  the  evidences  and 
results  of  liis  indefatigable  investigations.  lUit  to  us,  as 
opticians,  he  is  best  known  and  most  revered  for  having 
enriched  our  science  as  no  man  before  or  since  has  done,  and 
particularly  through  the  medium  of  his  great  work  on  the 
accommodation  and  refraction  of  the  eye,  the  fountain  of 
knowledge  from  which  every  writer  and  teacher  on  the  subject 
draws  his  inspiration. 

Bonder's  preference  in  his  work  was  always  for  teaching, 
and  he  is  said  to  have  possessed  in  an  eminent  degree  all  those 
essential  qualities  which  go  to  make  up  the  perfect  professor. 
"An  erudition  as  profound  as  extensive;  an  excellent  memory; 
an  intelligence  capable  of  adapting  itself  to  his  audience;  a 
wit  which  colors  abstract  matters;  a  rich  flow  of  language; 
a  voice  sonorous  and  flexible;  gesture  noble  and  significant; 
something  sublime  emanated  from  the  man;  physically  grand 
and  beautiful,  something  at  once  imposing,  captivating  and 
sympathetic;  great  knowledge  and  great  desire  to  impart  it." 

DOXDERS'   IMODESTV. 

It  seems  as  if  Bonders'  learning  was  equaled  only  by  his 
modesty,  and  the  latter  quality  is  scarcely  less  an  element  of 
greatness  than  the  former;  it  certainly  increases  one's  ad- 
miration for  the  man.  Several  instances  exemplifying  this 
trait  of  his  character  are  related,  and  they  are  so  distinctive  of 
the  man  as  to  bear  repetition. 

On  one  occasion  an  admirer  was  felicitating  him  on  the 
discovery  of  astigmatism,  w-hen  he  made  the  following  mag- 
nificent reply;  "Pardon  me,  my  friend,  astigmatism  was 
known  a  long  time  before  my  day;  I  only  discovered  astig- 
matic people." 

When  the  time  came  for  Bonders,  on  account  of  the 
limitations  which  age  imposed  upon  him,  to  retire  from  the 
professor's  chair,  which  he  had  honored  for  so  many  years, 
it  was  made  an  occasion  of  paying  special  homage  to  his  merits 
by  his  countrymen,  pupils  and  admirers.  His  modest  response 
to  all  the  glory  which  was  sought  to  be  showered  upon  him 
was,  "Talk  not  to  me  of  my  merits,  but  congratulate  me  on 
mv  luckv  star." 


IIYPERMETROPIA.  15 

CHARACTERISTICS  OF  A  11  VI'ERMETROI'IC  EYE. 

Hypermetropia  may  be  looked  upon  as  a  congenital  de- 
fect, in  fact  the  statement  has  been  made  that  all  babies  are 
born  hypermetropic.  It  is  supposed  to  be  due  to  an  arrested 
development  in  the  formation  of  the  eye-ball,  which  may  vary 
from  the  slig-htest  degree  to  an  extreme  condition  of  small- 
ncss. 

The  hypermetropic  eye  differs  somewhat  from  an  em- 
metropic eye,  and  the  following  have  been  enumerated  as  some 
of  the  characteristic  points  of  an  eye  suffering  from  this  defect. 
The  eye  is  said  to  look  smaller,  but  this  is  a  change  that  is 
not  always  noticeable,  although  as  a  matter  of  fact  the  ball 
is  smaller  than  the  normal  eye  in  all  of  its  dtmensions,  but 
particularly  antero-posteriorly.  The  lens  and  iris  advance  for- 
ward, which  makes  the  anterior  chamber  shallow^er.  Tlie 
pupil  is  small  and  contracted. 

The  ciliary  muscle,  by  reason  of  its  action  on  the  accom- 
modation, upon  which  the  eye  depends  for  whatever  clear 
vision  it  may  enjoy,  is  much  larger  and  more  fully  developed 
than  in  emmetropia,  this  development  being  particularly 
noticeable  in  the  anterior  portion,  which  is  composed  chiefly 
of  circular  fibers,  and  is  due  to  the  constant  strain  imposed  on 
the  accommodation  by  the  hypermetropia. 

On  account  of  the  constant  relation  existing  between  the 
accommodation  and  the  convergence  (as  has  been  fully  ex- 
plained in  the  previous  chapters)  this  excessive  accommoda- 
tion is  apt  to  cause  an  excessive  convergence,  the  result  being 
a  case  of  convergent  strabismus. 

In  hypermetropia  of  high  degree,  the  optic  nerve  is 
diminished  in  size  and  contains  a  less  number  of  fibers,  which 
accounts  for  the  lessened  acutcness  of  vision  so  often  found 
in  these  cases. 

In  this  defect  the  face  is  said  to  have  a  characteristic  flat 
appearance,  the  nose  depressed,  orbits  shallow,  and  the  dis- 
tance between  the  eyes  to  be  increased.  It  should  be  re- 
marked, however,  to  the  optician  that  these  points  are  often 
absent,  and  thai  there  may  be  no  distinctive  features  apparent 
in  the  face. 


16  HVPERMKTROPIA. 

It  is  not  unusual  to  find  a  liypermetropic  eye  disposed 
to  astigmatism. 

HYPERMETROPIA   HEREDITARY. 

It  is  not  an  infrequent  occurrence  to  find  many  members 
of  the  same  family  aifected  with  hypermetropia.  This  is  so 
commonly  the  case  that  when  the  diagnosis  of  hypermetropia 
is  reached  in  the  examination  of  a  patient,  the  question  natu- 
rally presents  itself  in  the  examiner's  mind  as  to  whether  some 
other  members  of  the  family  are  not  similarly  affected;  and 
when  this  question  is  put  to  the  patient,  the  answer  generally 
corroborates  the  assumption,  at  least  to  the  extent  of  admitting 
that  one  or  both  parents  commenced  to  wear  convex  glasses 
for  reading  at  a  very  early  age.  (Hypermetropia  in  some 
cases  first  shows  itself  as  an  early  presbyopia,  as  remarked  in 
the  last  chapter.) 

Cases  will  sometimes  be  met  with  in  which  one  eye  is  em- 
metropic, and  the  other  eye  hypermetropic;  and  in  such  cases 
there  may  be  a' very  marked  difference  in  the  form  of  the  bones 
on  the  two  sides  of  the  face,  thus  illustrating  the  shallowness 
of  the  orbits  and  the  flatness  of  the  face  with  the  diminished 
prominence  of  the  nose,  which  so  often  accompanies  and  in- 
dicates hypermetropia.  A  writer  relates  a  case  of  this  kind, 
the  patient  being  a  young  lady  who  presented  herself  for  treat- 
ment of  stricture  of  the  nasal  duct.  The  lack  of  symmetry 
between  the  two  sides  of  the  face  and  in  the  size  of  the  eye- 
balls was  strikingly  noticeable,  and  an  examination  showed 
the  presence  of  hypermetropia  in  one  eye. 

It  will  be  remembered  that  the  normal  or  emmetropic  eye, 
when  the  accommodation  is  at  rest,  is  accurately  adapted  for 
parallel  rays,  which  come  to  a  focus  on  the  retina,  forming  on 
this  membrane  sharply  defined  images  of  distant  objects,  from 
which  these  rays  emanate.  This  is  accomplished  without  any 
action  of  the  accommodation,  which  is  left  unrestricted  for 
its  normal  purpose  of  adjusting  the  dioptric  apparatus  of  the 
eye  for  the  divergent  rays  issuing  from  objects  close  at  hand. 

In  hypermetropia,  on  the  contrary,  we  find  the  dioptric 
system  of  the  eye,  when  the  accommodation  is  suspended  (this 
is  a  supposed  condition,  however,  and  one  that  seldom  occurs, 


IIVrKKMKTROriA.  17 

because  in  this  defect  the  acconiinodation  is  in  active  and  con- 
tinuous use),  on  account  of  the  shallowness  of  the  ball,  ar- 
ranged for  the  refraction  of  convergent  rays,  as  no  other  form 
of  rays  can  be  united  on  the  retina  in  the  production  of  a  clearly 
defined  image.  Now  it  is  a  well-known  fact  that  in  nature  all 
rays  of  light  are  either  parallel  or  divergent,  and  hence  the 
hypermetropic  eye,  being  conformed  for  convergent  rays,  is 
adapted  for  a  condition  which  does  not  naturally  exist. 

THE   FAR    POINT    IN    HYrERMETROPJA. 

In  emmetropia  the  far  point  of  distinct  vision  is  situated 
at  infinity,  or  at  any  distance  far  enough  removed  from  the  eye 
that  the  rays  proceeding  from  it  shall  be  parallel.  While  in 
hypermetropia,  on  account  of  the  adaptation  of  the  eye  for  the 
imnatural  convergent  rays,  the  far  point  is  negative,  or  may 
be  said  to  be  situated  beyond  infinity,  if  such  a  condition  can 
be  imagined. 

In  emmetropia  the  parallel  rays  are  united  on  the  retina, 
and  distinct  vision  is  the  result;  in  hypermetropia  these  same 
parallel  rays  strike  the  retina  before  they  have  converged  to 
a  focal  point,  which  renders  distinct  vision  an  impossibility, 
because  each  point  of  the  image  is  surrounded  by  diffusion 
circles,  and  these  circles  from  points  of  the  image  close  to- 
gether overlap  each  other. 

DEFINITION   OF  IIYFERMETROPIA. 

Hypermetropia  may  then  be  defined  as  that  condition  of 
the  eye  in  which  there  is  a  shortening  of  the  antero-posterior 
diameter  of  the  ball,  or  the  positive  refracting  power  of  the 
eye  is  deficient,  and  the  result  in  either  case  is  that  the  focus 
is  behind  the  retina.  Or,  in  other  words,  the  diameter  or 
length  of  the  eye-ball  is  less  than  the  focal  length  of  its  dioptric 
apparatus. 

THE     DIFFICULTIES     OF    HYPERMETROPIA     PRACTICALLY     DEM- 
ONSTRATED. 

A  concave  lens  is  a  negative  lens  and  diminishes  refrac- 
tion; a  hypermetropic  eye  is  one  in  which  there  is  naturally  a 
deficiency  of  refraction.     Now  if  we  consider  these  two  facts 


18  IIVl'KRMKTROPIA. 

together,  it  folk^ws  tliat  a  concave  lens  placed  before  an  em- 
metropic eye  will  lessen  its  refraction,  and  to  that  extent  will 
make  it  equivalent  to,  and  place  it  in  the  same  optical  condi- 
tion as,  a  hypemietropic  eye.  Therefore  if  any  one  enjoying 
emmetropic  eyes  desires  to  experience  a  practical  demonstra- 
tion of  the  difficulties  and  hindrances  which  are  ever  present  to 
annoy  and  harass  the  hypermetrope,  he  can  very  easily  place 
his  own  eyes  in  the  same  condition  by  making  them  artificially 
hypermetropic  by  the  use  of  concave  lenses. 

If  he  tries  first  weak  lenses,  and  by  changing  them  gradu- 
ally increases  their  strength,  he  will  in  the  beginning  find  that 
by  the  exercise  of  his  accommodation  he  is  able  to  neutralize 
and  overcome  the  diminishing  effect  of  the  concave  lenses. 


Outline  of  a  Hypermetropic  Eye,  Showing  the  Focus 
of  Parallel  Rays  to  be  Back  of  Retina. 

As,  however,  he  gets  into  the  higher  numbers,  it  becomes  a 
more  and  more  difificult  task  for  the  accommodation  to  coun- 
terbalance these  increasing  negative  lenses. 

If,  in  spite  of  these  warnings  that  the  accommodation  has 
reached  the  extreme  limit  of  its  powers,  and  its  greatest  effort 
is  required  to  preserve  vision  clear  through  the  concave  lenses, 
a  step  farther  be  taken  with  stronger  glasses,  it  would  entirely 
drain  all  the  resources  of  the  ciliary  muscles,  and  they  would 
be  no  longer  equal  to  the  task  of  supplying  the  necessary  re- 
fractive power,  and  vision  would  become  blurred,  and  the  eyes 
would  be  in  a  condition  of  absolute  hypermetropia. 

Convex  lenses  sufficiently  strong  placed  before  the  con- 
cave ones,  would  supplement  the  exhausted  accommodation, 
and  would  partly  or  wholly  nullify  the  diminishing  effect  of 
the  concave  lenses,  and  distant  vision  would  again  be  restored 
clear  and  distinct.  I 


IIYI'ERMETROPIA.  1^ 


FORMS  OF  HVPERMETROl'lA. 

Hypermetropia  ina\  l)c  classified  as  original  and  acquired. 

In  the  acquired  funn  the  eye  was  primarily  emmetropic, 
but  on  account  of  the  lessening  of  its  refraction,  toward  which 
all  its  senile  changes  tend,  the  focus  for  parallel  rays  falls  be- 
hind the  retina,  and  the  refraction  of  the  eye  passes  over  from 
a  condition  of  emmetropia  to  that  of  hypermetropia.  Tlie 
changes  that  take  place  in  the  eye  with  the  advance  of  years, 
more  especially  as  to  the  loss  of  accommodation,  and  the 
rationale  of  the  appearance  of  hypermetropia  in  old  age,  have 
been  fully  described  in  the  chapter  on  presbyopia. 

Original  hypermetropia  may  be  either  congenital,  or  de- 
veloped at  a  vc'rv  early  age  by  an  interruption  in  the  growth 


Ily 


icriiH'tropie  Eyo,  Sliowing  its  Adaptation 
for  Convergent  Rays. 


of  the  eye,  especially  in  its  antero-posterior  diameter.  The 
weight  of  authority  seems  to  favor  the  opinion  that  the  eyes 
of  new-born  babes  are  hypermetropic,  which  condition  may 
soon  develop  into  emmetropia,  and  then  pass  over  into  myopia ; 
and  when  once  these  changes  have  occurred  by  a  lengthening 
of  the  axis  of  the  eye-ball,  they  become  permanent,  and  the 
■eye  cannot  again  return  to  its  original  hypermetropic  condi- 
tion. This  would  indicate  a  tendency  for  the  eye-ball  to 
elongate,  and  the  natural  inference  would  be  that  myopia  is 
apt  to  increase,  while  hypermetropia  seldom  grows  greater, 
but  frcciuently  diminishes. 

T)lVISTOXS   OF   IIVPEKMETUOIMA. 

Original  hypermetropia  may  be  divided  into  manitcst  and 
lafcnt,  and  in  order  to  ascertain  the  total  hypermetropia  it  is 
iiecessarv  to  add  the  manifest  to  the  latent. 


20  HYPERMETROPIA. 

In  hypermetropia  of  not  too  high  a  degree,  it  is  usuall\- 
found  that  the  distant  vision  is  quite  up  to  the  standard,  and 
the  sight  is  apparently  that  of  an  emmetropic  eye.  This  is 
accomphshed  by  means  of  the  accommodation,  which  in- 
creases the  convexity  of  the  crystalhne  lens  and  adds  to  thc- 
refractive  power  of  the  eye,  and  thus  bends  parallel  rays  so  as 
to  advance  their  focus  from  behind  the  retina  on  to  this  struc- 
ture. It  is  the  same  effect  that  is  produced  by  a  convex  lens 
placed  in  fro^nt  of  the  eye;  and  the  amount  of  accommoda- 
tion required,  Nvhich  can  be  expressed  by  a  certain  number  of 
convex  lens,  will  represent  the  degree  of  hypermetropia 
present. 

The  division  of  hypermetropia  into-  manifest  and  latent 
depends  on  the  action  of  the  accommodation ;  manifest  hyper- 
metropia is  possible  only  with  a  suspended  accommodation,, 
w^hile  the  latent  form  is  that  which  is  concealed  by  the  con- 
traction of  the  ciliary  muscle.  Hence  it  follows  that  the  more 
passive  the  accommodation,  the  greater  the  manifest  hyper- 
metropia; and  the  more  active  the  accommodation,  the  greater 
the  latent  hypermetropia. 

The  manifest  hypermetropia  is  usually  apparent  without 
a  mydriatic,  and  is  measured  by  the  strongest  convex  glass 
that  will  be  accepted  for  distant  vision.  The  latent  defect  can 
be  made  manifest,  or  can  be  detected,  only  by  the  use  of  a  my- 
driatic. As  the  person  advances  in  life  and  the  power  of  ac- 
commodation weakens,  in  the  same  proportion  the  latent  defect 
decreases  and  passes  over  intO'  manifest,  until  finally  there  re- 
mains no  more  latent  trouble,  but  it  has  all  become  mani- 
fest. 

The  manifest  hypermetropia  is,  for  the  purposes  of  con- 
venience, written  Hm,  the  latent  hypermetropia  HI,  and  the 
total  hypermetropia  Ht. 

ILLUSTRATIONS    OF    THE    DIVISIONS    OF    HYPERMETROPIA. 

Perhaps  this  subject  can  be  made  more  clear  by  the  ex- 
emplification of  a  case  of  hypermetropia  tested  at  a  distance 
of  twenty  feet  with  Snellen's  test  types.  Possibly  the  eye  can 
distinguish  only  the  larger  letters,  and  the  vision  would  be 
recorded  as  follows:  V  =  iVV-     If  "O'W  there  is  placed  before 


HYPERMETROPIA.  21 

the  eye  a  convex  lens  of  2  D,  the  vision  is  raised  to  normal, 
and  V  =  |g.  In  this  case  the  accommodation  is  supposed  to 
be  at  rest,  and  the  total  hypermetropia  (Ht)  is  2  D. 

If,  however,  the  eye  would  call  into  action  a  portion  of  its 
accommodative  power,  the  hypermetropia  would  be  corrected 
thereby  and  the  vision  raised  to  |J  without  the  employment  of 
a  convex  lens,  and  this  is  usually  the  state  of  affairs  as  it  is 
found  in  young  hypermetropes.  If  now  the  eyes  are  tested 
with  convex  lenses,  the  vision  remains  the  same,  so  that  we 
hnd  \'  =  |§  either  with  or  without  convex  lenses.  This  illus- 
trates manifest  hypermetropia,  and  the  strongest  convex  lens 
through  which  vision  still  remains  |§  would  represent  the 
degree  of  manifest  hypermetropia  (Hm). 

Tlie  record  of  this  case  would  read  V  =  3^,  Hm.  =  +  i 
D.  That  is  to  say,  vision  is  normal  or  |g,  and  remains  as 
good  when  a  convex  lens  of  i  D  is  placed  before  the  eye. 
Now  in  this  case  we  presume  that  a  certain  amount  of  the 
defect  is  latent  or  concealed  by  the  action  of  the  accommo- 
dation, because  the  patient  is  unable  to  completely  relax  it. 

In  this  imaginary  case  we  have  a  total  hypermetropia  of 
2  D..  and  a  manifest  hypermetropia  of  i  D.,  and  therefore  the 
difference  between  the  two  would  indicate  a  latent  hyper- 
metropia of  I  D. 

The  latent  hypermetropia  can  seldom  be  revealed  except 
"by  the  use  of  atropine,  and  we  would  remark  in  passing  that 
this  is  not  always  necessary  for  the  following  reason :  we  can 
scarcely  ever  give  a  glass  to  do  more  than  correct  the  manifest 
hypermetropia,  which  can  be  measured  without  the  use  of  the 
drug;  why  then  should  it  be  considered  essential  to  determine 
the  latent  defect,  which  after  all  will  not  bear  correction? 

THEORY   OF  THE   CORRECTION   OF   HYPERMETROPIA. 

It  would  be  theoretically  correct  to  place  before  hyper- 
metropic eyes,  convex  glasses  of  such  strength  as  to  com- 
pletely neutralize  the  error  of  refraction  and  correct  the  total 
hypermetropia,  thus  giving  to  parallel  rays  the  degree  of  con- 
vergence for  which  the  refractive  media  are  adapted,  and  in 
this  manner  obviating  the  necessity  for  calling  into  action  any 
part  of  the  accommodation  for  vision  of  distant  objects,  so  as 


22  IIVrERMETROriA. 

to  leave  the  entire  accommodative  power  unimpaired  for  the 
necessary  adjustment  of  the  eye  for  the  divergent  rays  proceed- 
ing from  small  objects  close  at  hand.  This  would  be  the  ideal 
method  of  correction  of  this  oftentimes  distressing  defect. 

Although  it  would  seem  to  be  the  proper  thing  in  hyper- 
metropia  to  prescribe  such  glasses  as  would  completely  cor- 
rect the  defect,  yet  practically  such  a  method  of  procedure  has 
been  found  not  to  answer,  except  in  but  few  cases,  and  even 
then  not  until  after  repeated  trials  with  glasses,  and  not  until 
the  eyes  have  adapted  themselves  to  their  use. 

THE    OBSTACLE    IN    THE    WAY    OF    THE    COMPLETE    CORRECTION 
OF  HYPERAIETROPIA. 

The  hypermetropic  eye,  ever  since  it  commenced  to  fulfill 
its  function  in  looking  at  the  lettered  blocks  and  picture  books 
of  childhood  has  been  accustomed  to  associate  with  the  act  of 
vision  a  certain  amount  of  muscular  action,  or,  in  other  words^ 
a  definite  contraction  of  the  ciliary  muscle  to  overcome  the 
defect,  for  only  by  this  means  is  the  hypermetropic  eye  able 
to  enjoy  clear  and  distinct  vision;  and  as  the  natural  instinct 
of  the  eye  impels  it  to  produce  Avell-defined  vision  if  within 
the  range  of  its  possibility,  this  effort  of  the  muscle  of  accom- 
modation is  purely  an  automatic  and  involuntary  one,  and  is 
ever  present,  from  the  time  the  dawn  of  morning  opens  the 
eyelids  and  allows  the  rays  of  light  to  enter  through  the  re- 
fractive media,  until  they  are  closed  in  sleep. 

It  has  been  said  that  man  is  a  creature  of  habit,  which 
becomes  to  him  a  second  nature,  and  fromi  which  it  is  dif^cult 
and  oftentimes  impossible  for  him  to  break  away.  The  habit 
thus  acquired,  of  contraction  of  the  ciliary  muscle  coincident 
with  the  act  of  vision,  is  hard  to  abandon  entirely,  even  after 
the  error  of  refraction  is  fully  corrected  by  convex  glasses 
placed  before  the  eyes  and  all  necessity  for  the  use  of  the  ac- 
commodation thus  removed. 

Hence  it  follows  if  there  is  a  correction  (either  partial  or 
entire)  of  the  hypermetropia  by  means  of  the  accommodation, 
and  in  addition  there  is  a  correction  of  the  same  defect  by 
means  of  convex  glasses,  there  is  evidently  a  surplus  of  correc- 


IIYPERMETROriA.  i.r 

tion,  and  the  i^lasses  appear  to  be  too  strong  and  cannot  be 
worn. 

In  other  words,  we  are  able  to  correct,  by  the  employment 
of  glasses,  only  that  portion  of  the  hypermetropia  which  the 
accommodation  by  its  relaxation  will  permit  us  to  do,  or  which 
we  can  coax  the  accommodation  not  to  correct,  and  this  brings 
us  back  to  the  point  from  which  we  started  and  which  we 
emphasized  in  the  last  issue,  that  we  can  scarcely  ever  give  a 
glass  to  do  more  than  correct  the  manifest  hypermetropia. 

lUARRlXG   OF   IMAGES   DUE  TO   THE   SCREEN   I'.EIXG   TOO    CLOSE 
TO    THE    REFRACTIVE   MEDIUM. 

In  hypermetropia  the  focus  of  parallel  rays  is  behind  the 
retina,  and  hence  the  rays  strike  the  retina  before  they  have 
been  united  in  a  focal  point,  the  reason  being  that  the  retina 
(or  the  screen  on  which  the  images  are  formed)  is  closer  to 
the  crystalline  lens  than  the  focal  distance  of  the  dioptric  media 
of  the  eye. 

Any  student  of  optics  who  is  sufficiently  interested  in 
these  matters,  can  take  a  strong  convex  lens  from  his  trial  case 
and  see  for  himself  how  the  images  of  objects  will  be  blurred 
when  the  screen  on  which  they  are  formed  is  closer  than  the 
focal  distance  of  the  lens. 

The  student  will  stand  in  front  of  a  window  and  hold  the 
lens  in  such  a  position  that  the  light  coming  from  the  outside 
will  fall  upon  it  and  pass  through  it.  A  sheet  of  white  paper 
is  to  be  used  for  a  screen  and  placed  at  the  focal  distance  of 
the  lens.  If  the  strength  of  the  latter  is  5  D.,  the  sheet  of  paper 
will  be  placed  eight  inches  from  it,  and  small  and  distinct 
images  of  external  objects,  such  as  trees  and  houses,  will  be 
formed  upon  it;  every  detail  of  the  objects;  every  leaf  and 
branch  of  the  tree,  all  the  doors  and  windows  of  the  house, 
will  be  clearly  defined,  and  form  a  beautiful  (though  dimin- 
ished and  inverted)  picture.  Tliis  illustrates  the  fomiation  of 
distinct  images  on  the  yellow  spot  of  the  emmetropic  eye. 
the  retina  being  at  the  exact  focal  distance  of  the  dioptric 
system  of  the  eyes,  which  may  then  be  said  to  be  ix  me/VSURe. 

If  now  the  screen  of  white  paper  be  moved  slightly,  so  as 
to  bring  it  closer  to  the  lens,  the  sharpness  of  tlie  images  is 


24 


at  once  (lestroycd;  the  trees  may  still  be  seen  in  blurred  out- 
lines and  the  shape  of  the  house  be  discerned,  but  none  of  the 
fine  details  can  be  perceived.  If  the  screen  be  moved  still 
nearer,  the  trees  will  gradually  fade  out  of  sight,  and  even  the 
outlines  of  the  house  will  be  lost.     'Jliis  illustrates  the  fornia- 


Decembek.  1^6", 


liimgo  as  Formed  on  tlic  K( 


<if  llie  ICiniiiotriinii'  Eye. 


tion  of  the  indistinct  images  on  the  yellow  spot  of  the  hyper- 
metropic eye,  the  eye-ball  being  flat  and  the  retina  too  close 
to  the  crystalline  lens,  which  may  then  be  described  as  an  eye 
out  of  measure.  The  flatter  the  eye,  the  closer  the  retina  to 
the  crystalline  lens,  and  the  higher  the  degree  of  hyper- 
metropia,  the  more  blurred  will  be  the  images  formed  in  the 
eye,  and  the  less  satisfactory  the  vision. 


IIYPERMETROPIA.  Zo 

KliSTOKATION   OV  THE  CLEARNESS  OF  THE  IMPERFECT   IMAGES. 

When  the  screen  of  paper  is  moved  up  to  seven  inches, 
the  images  are  noticeably  blurred,  and  when  it  is  moved  to  six 
inches  there  is  no  distinct  definition  of  objects.  If  at  this  dis- 
tance a  second  convex  lens  of  1.50  D.  be  placed  before  the 
first  lens  of  5  D.,  an  instantaneous  and  marvelous  effect  is 


The  Imago  as  Formed  on  the  Retina  of  the  Hypermetropic  Eye. 


produced  in  the  restoration  of  the  images  to  perfect  clearness 
and  distinct  definition,  a  stepping,  as  it  were,  from  twilight 
to  mid-day. 

The  student  who  performs  this  experiment  for  himself 
will  be  the  better  able  to  understand  and  appreciate  the  effect 
of  convex  glasses  in  the  correction  of  hypermetropia,  and  how 
?.hey  produce  distinct  images  on  the  retina  without  any  accom- 
modative effort. 


26 


PRACTICAL    ILTA'STHATIOXS    Ol      I  1 1  1-:    DIS'I'IXCT    IMAf.KS    OF    KM- 

.AtKTROriA    AND     IIII':     INDISTINCT     IMACiKS 

OF    mi'KRMETROPIA. 

In  order  to  eniphasize  these  points,  and  to  afford  a  prac*:- 
cal  illustration  of  the  marked  difference  in  the  clearness  of  the 
imagoes  formed  in  the  emmetropic  and  hypermetropic  eyes,  as 
well  as  to  show  the  difficulties  under  wliich  the  hypermetrope 
labors,  wc  present  on  page  24  a  cut  of  the  title  page  of  a 
holiday  number  of  Tin-:  Kevstoxf  as  its  image  would  appear 
when  formed  on  the  yellow  spot  of  the  emmetropic  eye,  which 
the  reader  can  compare  with  the  image  of  the  same  object 
formed  in  the  hypermetropic  eye  on  page  25. 

The  first  cut  was  made  with  the  dioptric  ai>paratus  of  tiie 
photographic  camera  in  perfect  adjustment,  so  that  the  rays 
proceeding  from  the  title  page  were  accurately  focused  on  the 
screen.  In  making  the  second  cut,  the  screen  was  moved 
closer  to  the  condensing  lens  of  the  camera,  thus  stimulating 
the  relative  positions  of  the  retina  and  crystalline  lens  in  the 
hypermetropic  eye.  and  in  this  case  the  rays  struck  the  screen 
before  they  were  united  in  a  focus,  and.  as  a  consequence, 
the  image  there  formed  is  imperfect  and  indistinct. 

These  illustrations  have  reference  to  the  refractive  con- 
dition of  the  emmetropic  and  hypermetropic  eyes,  that  is,  with: 
the  eyes  in  a  state  of  rest  and  the  function  of  accommodation 
in  a  passive  condition.  The  student  knows  that  if  the  ac- 
commodation is  brought  actively  into  play,  the  result-  ob- 
tained will  be  entirely  different. 

The  hypermetrope,  if  the  degree  of  defect  be  not  too  high, 
by  the  exercise  of  his  accommodative  power  is  able  to  supple- 
ment and  increase  the  refractive  strength  of  his  eye,  and  in 
this  way  bring  the  focus  of  parallel  rays  forward  so  as  to  coin- 
cide with  the  retina,  and  thus  counteract  the  disturl)ing  intiu- 
ence  caused  by  the  nearness  of  the  retina  to  the  lens. 

This  would  clear  up  the  retinal  image  and  give  the  hyper- 
metrope perfect  vision,  but  it  would  be  accomplished  only  at 
the  expense  of  a  constant  strain  on  the  accommodation,  which 
Nature  will  not  sanction,  as  she  expects  distant  vision  to  be 
entirelv  devoid  of  accommodative  effort. 


IIYPERMETROriA.  4\ 

SUB-DIVISIONS  OF  HVPERMETROPIA. 

Manifest  hypennetropia  has  been  further  divided  into- 
facultative,  relative  and  absolute.  We  do  not  attach  very  nnicli 
practical  vakie  to  these  sub-divisions,  but  we  feel  that  our 
readers  should  not  be  entirely  ignorant  of  them. 

Facultative  hypermetropia  is  the  term  applied  to  those 
cases  of  hypermetropia  in  which  distant  objects  can  be  clearly 
seen,  either  without  or  with  convex  glasses.  In  these  cases 
the  accommodation  is  suf^ciently  strong  to  overcome  the  de- 
fect and  afTord  perfect  vision;  and  at  the  same  time  it  is 
obliging  enough,  when  convex  glasses  are  placed  before  the 
eyes,  to  subside  and  retire  from  the  field,  and  allow  the  convex 
lenses  to  do  its  work. 

Relative  hypermetropia  is  the  term  applied  to  those  cases 
of  hypermetropia  in  which,  by  the  addition  of  the  entire  ac- 
commodative force  to  the  natural  refractive  condition,  the  eye 
still  does  not  possess  sufficient  power  to  bring  the  parallel  rays 
of  distant  vision,  much  less  the  divergent  rays  of  near  vision, 
to  a  focus  on  the  retina,  except  by  an  over-convergence  of  the 
visual  axes,  or,  in  other  words,  by  squinting. 

Absolute  hypermetropia  is  the  term  applied  to  those  cases 
where  distinct  vision  is  impossible  without  artificial  assistance. 
The  entire  refractive  and  accommodative  power  of  the  eye,  re- 
inforced by  the  strongest  efTort  of  convergence,  is  insufficient 
to  bring  parallel  rays  of  light  to  a  focus  on  the  retina,  much 
less  the  divergent  rays  proceeding  from  near  objects.  Such 
an  eye  is  entirely  dependent  upon  convex  glasses  for  any  vision 
at  ail. 

The  facultative  form  of  hypermetropia  is  most  common 
in  youth,  when  the  accommodation  is  vigorous  and  able  to 
overcome  the  defect.  The  relative  form  occurs  a  little  later  in 
life,  when  the  accommodation  weakens  and  no  longer  suffices 
to  correct  the  defect  without  the  added  assistance  of  the  con- 
vergence. In  old  age  the  accommodation  has  become  entirely 
exhausted,  and  then  the  hypermetropia  becomes  absolute. 

From  the  very  nature  of  it,  acquired  hypermetropia  can 
never  occur  in  the  latent  form,  but  it  is  always  manifest. 
Neither  can  it  come  under  the  head  of  facultative,  but  it  maj- 


■2S  IIYPERMETROI'IA. 

possibly  be  relative,  although  it  is  more  apt  to  be  absolute. 
All  this  becomes  clear  and  easily  explained  when  it  is  remem- 
"bered  that  acquired  hypermetropia  is  due  to  a  natural  diminu- 
tion of  refraction,  and  occurs  only  after  the  accommodation 
Tias  been  shorn  of  its  strength  by  age,  and  when  all  that  re- 
inains  of  it  is  memory. 

Facultative  hypermetropia  is  almost  the  same  as  manifest 
liypermetropia ;  although  we  consider  the  latter  term  prefer- 
able because  it  is  more  expressive,  the  word  itself  indicating 
that  it  is  not  concealed,  but  that  it  is  easy  of  detection,  by  the 
.ready  acceptance  of  a  convex  lens, 

CAUSES   OF  HYPERMETROPIA. 

As  has  already  been  shown,  the  essential  condition  in 
liypermetropia  is  that  the  retina  is  too  close  to  the  dioptric 
apparatus,  so  that  the  rays  of  light  strike  this  membrane  in 
•dififusion  circles  before  they  have  had  the  opportunity  to-  unite 
in  a  focus.  This  condftion  may  be  dependent  upon  several 
'dififerent  causes,  which  we  will  enumerate  as  follows : 

1.  -\xial  hypermetropia,  in  which  the  dioptric  system  may 
measure  up  to  the  same  standard  as  an  emmetropic  eye,  but 
the  eye  is  flat  and  there  is  a  lessening  of  the  antero^posterior 
diameter  of  the  globe  of  the  eye,  and  a  consequent  shortening 
of  its  axis.  This  is  by  far  the  most  common  cause,  and  it  has 
'been  illustrated  in  the  earlier  part  of  the  chapter. 

The  axial  form;  of  hypermetropia  is  congenital,  and  is  due 
to  an  arrest  of  development  of  the  eye  in  its  growth,  particu- 
larly noticeable  in  the  antero-posterior  diameter.  Such  eyes 
are  distinguished  by  their  smallness  and  mobility,  the  diminu- 
tion in  size  being  oftentimes  a  noticeable  feature. 

2.  The  length  or  depth  of  the  eye-ball  may  be  the  same 
as  an  emmetropic  eye,  but  the  refractive  power  of  the  dioptric 
apparatus  may  be  too  feeble  to  bring  the  rays  of  light  to  a 
focus  on  the  retina,  which  they  strike  in  un-united  circles,  pro- 
•ducing  the  same  effect  as  the  axial  form. 

This  deficiency  of  rcfracfiz'C  pozver  may  be  due  to  several 
•different  causes:  there  may  be  a  depression  of  the  cornea  or 
a  lessening  of  its  convexity,  as  the  result  of  inflammation  or 
•disease;  or  it  may  normally  be  lacking  in  convexity;  there 


HYPERMETROPIA.  29 

may  also  be  a  diminution  in  the  natural  convexity  of  the  crys- 
talline lens;  and  there  may  also  be  a  reduction  in  the  index 
of  refraction  of  the  refracting  media,  the  aqueous  humor,  the 
crystalline  lens  and  the  vitreous  humor. 

3.  Aphakia,  or  the  absence  of  the  crystalline  lens  either 
naturally  or  artificially,  is  a  cause  of  the  most  pronounced 
hypermetropia.  In  such  cases  there  is  an  absence  of  all  re- 
fractive power  and  the  eye  becomes  intensely  hypermetropic. 

AMOUNT  OF  SHORTENING  IN  AXIAL  HYPERMETROPIA. 

The  following  table  (after  Bonders)  shows  the  amount 
of  shortening  of  the  axis  of  the  eye-ball  for  the  various  de- 
grees of  hypermetropia: 


Degree 

Diminution 

of  Hypermetropia. 

of  Axial  Line. 

50  D. 

.16 

p  mm. 

I 

D. 

•31 

mm. 

I. 

50  D. 

•47 

mm. 

2 

D. 

.62 

mm. 

2. 

50  D. 

•77 

mm. 

3 

D. 

.92 

mm. 

3-50  D. 

1.06 

1  mm. 

4 

D. 

1.22  mm. 

4-50  D. 

1.4 

mm. 

5 

D. 

1.6 

mm. 

6 

D. 

1-9 

mm. 

7 

D. 

2.2 

mm. 

8 

D. 

2.6 

mm. 

9 

D. 

2.9 

mm. 

10 

D. 

3-2 

mm. 

II 

D. 

3-3 

mm. 

12 

D. 

3-4 

mm. 

13 

D. 

3-5 

mm. 

14 

D. 

3.7 

mm. 

15 

D. 

4- 

mm. 

16 

D. 

4.2 

mm. 

17 

D. 

4.4 

mm. 

18 

D. 

4.6 

mm. 

19 

D. 

4.7 

mm. 

20 

D. 

4-9 

mm. 

The  axial  line  of  the  emmetropic  eye  is  nearly  ^;-;  of  an 
inch;  in  3.50  D.  of  hypermetropia  this  would  be  reduced  to 
^f  of  an  inch;  in  7  D.  of  hypermetropia  to  |^,  and  in  10  D. 
of  hypermetropia  to  ff  of  an  inch.  Tliis  shows  in  the  latter 
grade  of  the  defect  a  shortening  of  ^  inch,  which  is  quite  a 
considerable  amount. 


•30  IIVPERMETKOPIA, 

PRENALIiNXi;    OF    H VrKKMKTROPIA. 

llypcrmctropia  is  the  predominant  error  of  refraction. 
Babies  in  the  majority  of  cases  are  bom  hypermetropic  (per- 
haps in  all  cases),  althoug-h  this  condition  may  afterward  de- 
velop into  emmetropia,  and  finally  pass  over  into  myopia. 
The  reason  why  infants  are  almost  invariably  hypermetropic 
is  undoubtedly  due  to  the  fact  that  at  birth  the  eye  has  scarce 
reached  its  full  development. 

\'arious  animals,  such  as  frogs,  rabbits,  cats  and  dogs, 
have  been  examined  with  the  ophthalmoscope  to  determine 
their  refraction,  and  all  have  been  found  to  be  hypermetropic, 
sometimes  as  much  as  3  D.  or  4  D.  The  ciliary  muscle  in 
these  animals  is  but  poorly  developed,  the  hypermetropia 
therefore  existing  in  a  manifest  form;  in  view-  of  which  their 
near  vision  must  be  ver\'  indistinct.  This,  ho\vever,  is  a  mat- 
ter of  no  inconvenience  to  them,  as  they  are  not  called  upon  to 
use  their  eyes  in  near  vision  for  those  employments  which  so 
nmch  tax  the  human  eye,  reading,  writing  and  sewing. 

DEGREE  OF  HYPERMETROPIA. 

Ordinarily  the  degree  of  hypermetropia  may  be  expressed 
by  the  convex  lens  that  is  required  to  correct  it.  In  a.vuil 
hypermetropia  it  depends  upon  the  flatness  of  the  eye,  or  the 
distance  of  the  retina  from  the  focus  of  the  refracting  media. 

In  refractive  hypermetropia  it  depends  upon  the  deficiency 
of  refractive  power,  or  the  amount  to  which  this  falls  below 
the  normal  standard. 

In  emmetropia  the  distance  of  the  retina  and  the  location 
of  the  principal  focus  exactly  coincide,  and  the  extent  of  their 
departure  from  each  other  in  hypermetropia  would  indicate 
its  degree,  and  the  greater  this  departure  the  higher  the  degree 
of  defect.  In  one  case  we  reckon  the  distance  from  the  nodal 
point  to  the  focus  of  the  hypermetropic  eye,  and  the  distance 
from  the  nodal  point  to  the  retina  of  the  same  eye.  and  then 
compare  the  two.  and  the  difference  between  them  will  denote 
the  hypermetropic  deficiencw 

In  the  table  given  we  can  see  the  amount  of  diminution 
of  the  axial  line  for  every  dioptric   of  hypermetropia,   and 


IIYPERMKTROI'IA.  31 

conversely  a  certain  diniinution  in  the  axial  line  implies  a  cer- 
tain degree  of  hypernietropia,  ami  each  increases  in  equal  pro- 
^xwtion.  A  convex  lens  corresponding  to  the  grade  of  the  de- 
fect will  bring  forward  the  focus  to  the  position  of  the  retina, 
and  thus  tend  to  counterbalance  the  diminution  in  the  axial 
line.  While  in  refractive  hypernietropia,  the  convex  len.s  di- 
rectly supplies  the  deficiency  in  refractive  power,  and  at  the 
same  time  reveals  its  extent  and  expresses  it  in  definite  terms 
i»f  refraction. 

A  good  idea  of  the  difference  in  shape  between  the  em- 
metropic eye  and  the  hypermetropic  eye  may  be  obtained  by 
■comparing  a  round  apple  with  a  flat  turnip.  The  round  apple 
represents  the  normal  or  emmetrcpic  eye.  and  the  turnip  the 
flat  or  hypermetropic  eye,  and  a  comparison  of  them  will  con- 
vey to  the  mind  a  well-defined  conception  of  the  difference  in 
shape  between  cmmctropia  and  hypernietropia. 

svMPTo^rs  of  hypermetropia. 

When  a  child  complains  of  headache  and  pain  in  the  eyes, 
-and  is  taken  from  school  and  charged  with  stupidity,  or  pun- 
ished for  idleness,  and  the  family  physician  advises  abstinence 
from  study  or  change  of  occupation,  and  puts  the  patient 
through  a  course  of  powerful  medicines  or  (puts  a  course  of 
medicines  through  him)  for  an  imaginar}-  nervous  trouble,  the 
intelligent  optician  will  recognize  these  as  symptoms  of  hyper- 
metropia; and  he  knows  (and  why  shouldn't  the  family  physi- 
cian know?)  that  medicines  are  worse  than  useless  in  such  a 
case.  I)ut  that  a  pair  of  properly  adjusted  convex  glasses  will 
remove  the  headache  and  pain  in  the  eyes  (when  nothing  else 
can),  and  will,  perhaps,  make  the  child  as  bright  and  studious 
as  any  of  his  companions.  Otherwise  if  the  cause  of  the 
trouble  is  not  recognized  and  rectified,  the  child's  prospects 
are  blighted  for  life. 

The  hypermetrope  (if  the  defect  is  not  of  too  high  degree) 
usually  sees  well  at  a  distance,  but  the  presence  of  the  defect  is 
made  known  even  in  early  life,  by  the  pain  and  symptoms  of 
fatigue  that  follow  any  close  use  of  the  eyes.  By  a  tension  of 
the  accommodation  the  hypermetrope  may  be  able  to  read  well 
for  awhile,  but  sooner  or  later  the  constant  effort  to  contract 


33  llYI'F.RMHTROriA. 

the  muscle  of  acconiniodation  sufficiently  for  near  work  causes 
fatigue  and  exhaustion  of  the  muscle,  and  the  accommodative 
effort  can  be  maintained  only  by  the  greatest  difficulty,  and 
the  patient  is  reminded  that  he  has  eyes  and  that  they  arc  weak 
and  painful  ones. 

The  eyes  feel  strained  and  painful,  the  letters  run  together 
and  become  blurred,  and  there  is  an  instinctive  desire  to  rest 
the  eyes  by  closing  them  for  a  moment  or  two  and  compress- 
ing them.  After  this  a  fresh  start  can  be  made,  only  to  break 
down  in  a  little  while  as  before.  In  short,  the  symptoms  of 
hypermetropia  may  be  said  to  consist  of  pain  and  discomfort 
on  using  the  eyes,  and  an  indistinctness  of  the  letters  on  a 
printed  page. 

SELF   CORRECTION    OF   HYPERMETROPIA. 

The  condition  of  every  hypermetrope  would  be  a  sorry 
one  indeed,  if  he  could  not  alter  and  increase  the  refraction 
of  his  eye,  and  make  vision  clear  and  distinct  by  bringing  the 
focus  of  rays  forward  to  the  retina.  While  a  hypermetrope 
wdth  no  inherent  power  over  the  defect  would  see  nothing 
clearly  at  any  distance,  fortunately  he  possesses  in  his  accom- 
modation a  means  by  which  he  can  increase  his  refraction  and 
overcome  his  trouble.  While  it  is  possible  for  distinct  vision 
to  be  thus  purchased  by  the  hypermetrope,  it  is  accomplished 
only  at  the  expense  of  a  constant  strain  upon  the  accommoda- 
tion, the  amount  of  strain  depending  on  the  degree  of  hyper- 
metropia. 

Since  hypermetropia  can  be  thus  corrected  by  the  indi- 
vidual himself  by  the  use  of  his  accommodation,  no  ill  effects 
may  be  noticed  for  some  time,  and  indeed  the  presence  of  the 
defect  may  not  even  be  suspected.  At  length  there  comes  a 
time  when  the  accommodation  breaks  down,  and  it  is  no  longer 
equal  to  long-sustained  efforts  required  by  reading  and  near 
work. 

Anything  that  weakens  the  accommodation  will  pre- 
cipitate this  breakdown,  hence  it  is  especially  liable  to  show 
itself  after  a  protracted  illness,  or  if  the  patient's  system  has 
been  run  down  from  overwork  or  anxiety.  It  also  becomes 
apparent  as  the  patient  approaches  the  presbyopic  period  of 


IlvrEKMKTROriA.  33 

life,  when  tlic  acconinuulation  fails  from  the  natural  cliang-es 
in  the  eye. 

The  illustratiun  previously  given,  showing  the  outline  of 
a  hypermetropic  eye,  represents  it  as  refracting  parallel  rays 
of  light,  or  those  proceeding  from  a  distance  of  twenty  feet  or 
more,  in  which  case  the  focus  is  behind  the  retina  and  vision 
is  more  or  less  indistinct.  As  has  just  been  described,  this 
focus  is  advanced  to  the  retina  and  vision  made  clear  by  the 
action  of  the  acconunodation,  which  is  thus  kept  on  a  constant 
strain. 

But  when  the  rays  proceed  from  close  objects  or  from 
those  nearer  than  twenty  feet,  they  became  divergent,  and  the 
nearer  the  object  is  brought  to  the  eye,  the  more  divergent 
the  rays  that  proceed  from  it  to  enter  the  eye.  Now  it  does 
not  require  much  reasoning  to  show  that  when  divergent  rays 
are  refracted  by  a  lens,  the  resulting  focus  cannot  be  at  the 
same  place  as  that  of  parallel  rays,  but  it  will  be  farther  re- 
moved; or  if  it  is  desired  to  keep  the  focus  at  the  same  place, 
it  is  equally  evident  that  more  power  is  necessary  in  a  lens  to 
focus  divergent  rays  at  that  point  than  is  required  to  bring 
])arallcl  rays  to  a  focus  at  the  same  distance. 

THE  ACCOMMODATION  IN  IIYrERMETROPIA. 

Hence  when  we  apply  these  principles  to  the  hyper- 
metropic eye,  we  find  that  the  focus  of  divergent  rays  is  back 
of  that  of  parallel  rays,  or  still  further  removed  from  the  retina, 
when  the  accommodation  that  is  in  force  for  distance  remains 
unchanged.  Therefore  the  accommodation  of  the  hyper- 
metrope,  which  must  be  constantly  exerted  even  for  distance, 
is  put  to  a  still  greater  strain  for  near  vision. 

As  a  consequence,  it  follows  in  reading,  w-riting  or  sewing, 
to  which  the  emmetrope  comes  with  fresh  and  strong  eyes, 
that  in  the  case  of  the  hypermetrope,  who  is  compelled  to  use 
some  of  his  accommodation  for  distant  vision,  and  whose 
ciliary  muscle  is  in  the  harness  (as  it  were)  from  the  time  the 
eyes  are  opened  in  the  morning  until  they  are  closed  in  sleep 
at  night,  the  start  is  made  with  that  much  of  a  deficit  from  the 
normal  strength  of  the  eyes,  and  near  vision  is  maintained  and 
continued  only  by  calling  into  action  the  reserve  of  accommo- 


31  IIYPERMKTKOI'IA. 

'Jativc  power,  and  in  sonic  cases  the  totality  of  acconnnoila- 
tion  of  wliicli  the  eye  is  capable. 

THE    RESERVE    MUST    NOT    I)E    IMI'Al  KEl). 

Just  as  the  use  of  its  reserve  will  impoverish  a  bank  or  an 
insurance  company,  so  the  use  of  its  reserve  acconnnodativc 
power  will  exhaust  an  eye  and  cause  it  to  break  down;  for  it 
must  be  remembered  that  a  tension  of  only  a  portion  of  the 
accommodation  can  be  sustained  for  any  length  of  time. 
Therefore  in  the  case  of  the  hypermetrope,  who  is  compelled  to 
use  a  part  of  his  accommodation  for  distance  and  the  balance 
oi  it  for  reading,  there  soon  appear  pain  and  fatigue  of  the  eyes 
and  general  symptoms  of  asthenopia,  which  gradually  increase 
and  become  so  pronounced  as  to  compel  a  frequent  interrup- 
:ion  of  the  strain  on  the  accommodation  by  closing  the  eyes 
and  resting  them  for  a  moment  or  two. 

The  laws  of  State  prohibit  the  officers  of  a  bank  or  an 
insurance  company  from  touching  the  reserve  fund,  which 
must  be  kept  intact,  under  heavy  penalties;  but  not  more  so 
ihan  do  physical  laws  forbid  any  encroachment  on  the  reserve 
■of  accommodative  power,  else  equally  severe  punishment  may 
follow.  As  a  rule,  banks  and  insurance  companies  are  so  con- 
servatively managed  that  not  only  is  the  reserve  not  infringed 
upon,  but,  on  the  other  hand,  it  is  from  time  to  time  increased, 
and  to  that  extent  is  the  institution  inherently  strengthened 
and  raised  in  public  estimation.  Rectitude  of  character,  as 
well  as  fear  of  the  law,  averts  any  violation  of  the  reserve  in 
banks  and  insurance  companies,  except  in  rare  instances,  when 
-.he  offender  is  forced  to  pay  the  penalty  for  his  crimes.  But 
no  high  sense  of  duty  to  one's  self,  nor  even  the  fear  of  the 
suffering  that  is  sure  to  follow^  prevents  violation  of  the  laws 
of  health,  as  is  noticeably  evidenced  on  every  liand  by  the 
abuse  of  the  eyes  and  of  the  stomach.  The  hypermetropic  eye 
is  urged  to  the  full  extent  of  its  accommodative  power,  until 
it  breaks  dow^n  from  sheer  exhaustion,  while  the  stomach  is 
overloaded  at  all  hours  of  the  day  and  night  with  rich  and 
indig-estible  food,  until  it  finally  rebels  and  is  unable  to  perform 
its  functions. 


IIVPERMETROPIA.  35 

FAR-SIGHTEDNESS. 

The  popular  term  for  hypermetropia  is  far-sightedness  or 
long-sig-htcdness,  and  the  use  of  these  words  has  led  the  laity 
to  believe  that  such  eyes  can  see  better  at  a  distance  than  em- 
metropic eyes;  but  these  terms  are  misnomers  and  are  mis- 
leading, because  a  hypermetropic  eye  cannot  see  any  better  at 
a  distance  than  an  emmetropic  eye,  and  besides,  what  it  does 
see  is  only  at  the  expense  of  an  unnatural  use  of  the  accom- 
modation. The  student  who  understands  the  shape  of  the 
hypermetropic  eye,  and  the  difficulties  under  which  it  labors, 
will  realize  that  it  is  far  from  being  as  good  an  eye  as  the 
normal.  Then,  too,  it  frequently  happens  that  hypermetropia, 
if  of  high  degree,  very  much  diminishes  the  acuteness  of  vision. 

CONFOUNDED   WITH   MYOPIA.  ->^ 

On  account  of  this  impairment  of  vision,  hypermetropia    /► 

is  sometimes  mistaken,  even  by  the  patient  himself,  for  myopia. ) 

These  are  cases  of  hypermetropia  of  high  degree,  in  which  the 
person  finds  that  he  is  able  to  materially  improve  his  reading 
vision  by  holding  his  book  close,  which  increases  the  size  of 
the  retinal  image,  intensifies  the  illumination,  and  b}'  con- 
tracting the  pupil  cuts  ofif  some  of  the  circles  of  dififusion..  Is 
it  any  wonder  under  these  circumstances  that  the  case  is 
looked  upon  as  one  of  myopia?  These  matters  can  perhaps 
he  best  emphasized  by  a  few  illustrative  cases  taken  from  the 
Avriter's  record-book. 

A    CASE    OF    HYPERMETROPIA    SIMULATING    MYOPIA. 

William  F.  Aged  ten  years.  School-boy.  Comes  to 
me  with  the  statement  that  he  has  always  been  near-sighted, 
and  that  of  late  his  eyes  are  getting  worse.  They  hurt  when 
lie  reads,  and  vision  is  quite  indistinct,  so  much  so  that  he  is 
compelled  to  almost  close  his  lids  in  order  to  see.  There  is 
also  a  convergent  squint,  which  alternates  between  the  two 
«yes.  R.  V.  =  TjVi^,  L.  \''.  =  ,"1, „.  Reads  Jaeger  No.  9,  2  in. 
to  5  in. 

A  histor)'  such  as  this,  with  so  imperfect  near  and  distant 
vision,  is  very  apt  to  mislead  the  average  optician  into  sup- 


36  IIYPERMETROPIA. 

posing  that  he  had  a  case  of  myopia  to  deal  with;  and  really. 
to  any  but  a  skilled  refractionist,  this  would  be  a  most  natural 
error,  for  is  not  the  boy  compelled  to  hold  his  book  ver)-  close 
to  his  eyes,  and  is  not  his  distant  vision  imperfect  and  indis- 
tinct, and  does  he  not  half  close  his  eyelids,  as  all  myopes  are 
apt  to  do? 

In  testing-  his  eyes  with  convex  lenses,  I  soon  found  it 
was  a  case  of  high  hypermetropia,  but  vision  was  scarcely  sat- 
isfactory even  wnth  the  best  glasses  I  could  give  him.  As  this 
was  an  unusual  case,  and  as  he  desired  the  removal  of  the 
strabismus,  I  instilled  atropine  in  his  eyes  for  a  week,  during 
which  time  I  operated  on  his  eye  for  the  correction  of  the 
strabismus.  I  kept  him  under  observation  for  two  weeks,  and. 
then  ordered  the  following  glasses: 

L.  J  ■-'     '    for  constant  wear. 

Some  three  weeks  later  he  reports  eyes  as  comfortable, 
able  to  read  and  study  with  satisfaction,  and  does  not  have  to 
hold  book  so  near,  nor  half  close  lids,  in  reading,  as  formerly. 

ANOTHER   CASE    OF    IIYPERMETROPIA,    IN    WHICH    AN    OPTICIAN 
PRESCRIBES   CONCAVE   GLASSES. 

Annie  F.  Aged  seventeen  years.  A  sister  of  the  boy  iu 
case  above  narrated.  She  comes  with  nearly  the  same  history 
as  her  brother.  She  says  she  has  always  been  near-sighted^ 
but  does  not  have  much  pain  in  her  eyes  unless  she  uses  them 
for  too  long  a  time.  Some  months  ago-  she  purchased  a  pair 
of  glasses  from  an  optician  (which  she  showed  me,  and  which 
I  found  on  examination  to  be  —  3.50  D.),  but  they  have  been 
of  no  benefit  to  her  and  she  has  used  them  but  little.  R,  V. 
=  -jV^,  L.  V.  l^-jj.  Refraction  =  manifest  hypermetropia  of 
3.50  D.  Reads  Jaeger  No.  9,  2  in.  to  7  in.  With  +  3.50  D. 
can  read  the  same  print  out  to  1 1  in.     Prescribed  for  her 

R   ) 

L,.  J    •    ^'^        '  for  constant  wear. 

Two  months  later  she  reports  that  her  sight  has  improved 
very  much,  and  that  she  can  see  better  than  she  ever  could, 
and  is  now  able  tO'  use  her  eyes  a  great  deal,  without  pain  or 
discomfort. 


IIYPERMETROPIA.  37 


THE   MORAL  OF  THESE  CASES. 

One  lesson  to  be  learned  from  the  above  cases  is  that  too 
much  reliance  should  not  be  placed  on  the  patient's  statements. 
Both  the  boy  and  the  girl  called  themselves  near-sig-hted,  and 
they  both  accepted  concave  glasses  when  placed  before  their 
eyes.  Under  these  circumstances  nothing  is  more  natural  to 
the  unskilled  optician  than  to  regard  these  as  cases  of  myopia, 
and  hence  every  man  should  be  constantly  on  his  guard  to 
avoid  falling  into  such  a  grievous  error. 

The  reader  of  these  pages,  even  though  he  possesses  only 
a  moderate  amount  of  knowledge  and  experience,  is  aware 
that  to  give  concave  glasses  to  either  of  the  above  cases  would 
not  only  fail  to  relieve  them,  but  would  make  their  eyes 
infinitely  worse  than  to  wear  no  glasses  at  all,  it  would,  in  fact, 
only  be  adding  fuel  to  the  fire. 

In  the  boy's  case  he  came  to  me  at  first  hand,  and  I  was 
able  to  correctly  diagnose  the  trouble  and  prescribe  the  proper 
glasses,  and  hence  he  suffered  no  injury  to  his  eyes  from  im- 
proper lenses.  But  the  girl  ran  a  great  risk  of  ruining  her 
eyes  with  the  concave  glasses  that  were  prescribed  for  her,  and 
she  escaped  only  because  the  glasses  were  of  no  benefit  and 
she  did  not  wear  them. 

Another  interesting  point  that  impresses  us  in  the  study 
of  these  cases  is  the  occurrence  of  two  such  marked  cases  of 
hypermetropia  in  the  same  family. 

ANOTHER  CASE  OF   HYPERMETROPIA  SIMULATING   MYOPIA. 

Mary  H.  Aged  fifteen  years.  About  a  year  ago  her 
eyes  commenced  to  trouble  her.  She  consulted  an  oculist, 
who  told  her  it  was  necessary  to  drop  atropine  into  her  eyes, 
to  which  she  and  her  parents  objected.  She  was  then  taken 
to  another  oculist,  who  said  she  didn't  need  any  glasses. 

She  comes  to  me  with  the  statement  that  she  has  always 
held  her  book  close  to  her  eyes,  but  recently  is  compelled  to 
hold  it  closer  than  ever.  Complains  of  a  great  deal  of  head- 
ache, and  of  a  dull,  heavy  pain  over  eyes,  which  is  much 
worse  after  readinjr. 


38  IIYPERMETROriA. 

V.  =  11  Hm.  =  +  1.25  D.,  with  which  V.  =  1§.  Reads. 
Jaeger  3,  2^  in.  to  9  in.  With  the  +  1.25  glasses  the  range  of 
acconiniodation  is  from  3  in.  to  33  in.     Ordered 

R-  1  -!-  I  2=;  D 

Iv.  j    '      ■  ^      'for  constant  wear. 

Three  years  later  she  reports  that  glasses  have  given  the 
greatest  satisfaction  in  every  particular,  and  she  wants  them 
put  into  a  gold  frame. 

One  interesting  point  about  this  case  is  the  limited  range 
of  accommodation  for  so  small  a  degree  of  hypermetropia, 
and  the  wonderful  effect  of  the  glasses  in  increasing  her  read- 
ing limit  from  nine  inches  to  thirty-three  inches.  Cases  like 
this  are  afforded  untold  benefit  from  the  proper  glasses,  while 
at  the  same  time  they  are  a  source  of  great  satisfaction  to  the 
prescribing  optician. 

The  distance  of  the  far  point  in  this  case  (nine  inches) 
would  point  toward  myopia,  although  with  an  acuteness  of 
vision  of  5^  but  a  slight  degree  would  be  possible. 

ANOTHER   SIMILAR   CASE. 

'  Mrs.  Sarah  K.  Aged  thirty-eight  years.  Says  she  has 
been  near-sighted  all  her  life,  but  has  never  been  able  to  get 
glasses  to  suit  her  eyes. 

V.  =  -sVV-  Hm.  -f  5.50  D.,  with  which  V.  =  i§.  Can 
read  only  large  size  print,  and  can  read  no  farther  off  than 
seven  inches.  With  the  4-  5.50  D.  lenses  can  read  out  to 
twelve  inches.  As  these  glasses  correct  only  her  manifest 
hypermetropia,  and  as  she  is  approaching  the  presbyopic 
period,  she  will  consequently  need  a  stronger  pair  for  reading. 
After  testing  her  eyes  for  reading  I  ordered  R.  and  L.  -|-  8  D., 
which  afforded  her  the  greatest  satisfaction. 

The  point  of  interest  in  this  case  is  that  this  woman  should 
have  reached  thirty-eight  years  of  age  without  having  been 
able  to  obtain  suitable  glasses,  which  can  be  explained  on  oiie 
of  two  grounds :  Either  the  optician  gave  her  concave  glasses 
because  she  said  she  was  near-sighted,  which  would  only 
hinder  her  eyes  instead  of  helping  them;  or  he  did  not  know 
how  to  properly  test  her  eyes  for  hypermetropia,  and  hence 
gave  her  only  a  weak  convex  glass  of  not  sufficient  strength 


IIYPERMETROPIA.  39 

to  afford  her  relief,  because  he  was  afraid  he  niig-ht  injure  her 
eyes  by  giving'  her  too  strong  a  glass. 

ANOTHER     CASE     OF     II  VPERMETROriA,     CLASSED     AS     ONE     OF 
MYOPIA. 

Lizzie  H.  Aged  twenty-eight  years.  Says  she  has  al- 
ways been  near-sighted,  and  when  attending  school  the  teacher 
allowed  her  to  go  close  to  the  windows  in  order  to  be  able  to 
see  to  read.  On  examination  I  found  her  vision  ig,  and  with 
the  unassisted  eye  was  unable  to  read  even  the  largest  size 
print  on  the  reading  test  card.  A  pair  of  -f  8  D.  enabled  her 
to  read  ordinary  print  with  ease  and  comfort,  and  gave  her 
good  distant  vision, 

A  CASE  OF  IIYPERMETROPIA  TREATED  WITH  CONCAVE  GLASSES. 

Susan  G.  Aged  ten  years.  Complains  of  a  great  deal  of 
pain  in  eyes,  and  headache.  She  showed  me  a  pair  of  —  4  D. 
glasses  which  an  optician  had  given  her,  but  which  she  had 
not  been  able  to  wear.  She  cannot  see  at  a  distance  with  them, 
nor  can  she  read  with  them;  neither  can  she  read  without 
them,  as  her  eyes  have  gotten  into  such  a  weak  and  irritable 
condition.  An  examination  showed  her  vision  equals  ^^.  and 
a  manifest  hypermetropia  of  -j-  1.25  D.  Is  able  to  read  news- 
paper print  no  farther  away  than  nine  inches. 

As  the  girl  was  young  it  seemed  best  to  commence  with 
weak  lenses,  and  hence  she  was  ordered  -f  .75  D.  for  constant 
wear.  A  week  later  she  returned  to  have  the  glasses  set  in  a 
gold  frame,  and  her  report  was  that  they  had  given  the 
greatest  satisfaction ;  she  can  see  well  with  them  both  far  and 
near,  with  entire  relief  from  the  pain  in  her  head  and  eyes. 

The  error  of  the  optician  in  giving  this  young  girl  a  con- 
cave lens  of  4  D.  is  a  most  inexcusable  one.  It  is  difficult  to 
understand  how  such  a  mistake  could  have  been  made  by  an 
optician  of  any  intelligence,  except  on  the  supposition  that  it 
was  looked  upon  as  a  case  of  myopia,  and  the  concave  glasses 
were  prescribed  according  to  the  rule  in  myopia  that  the  dis- 
tance of  the  far  point  expresses  the  degree  of  defect  and  at  the 
same  time  the  correcting  glass. 


40  IlYPER^[KTRO^TA. 

1 1'  the  o]>tician  had  examined  her  distant  vision,  he  could 
hardly  have  made  such  an  error,  because  a  vision  of  ^^  is  not 
compatible  with  a  myopia  of  4  D.;  and  besides,  if  he  had 
measured  her  refraction  according-  to  the  methods  laid  down 
in  The  JMaxlat.,  he  would  certainly  have  found  some  evidence 
of  the  existence  of  hypcrmetropia;  at  least  nothing  to  lead  him 
to  ])rescribe  a  —  4  D.  glass.  A  grievous  error  of  this  kind 
would  permanently  injure  the  eyes  if  the  patient  continued  to 
wear  the  glasses,  and  when  discovered  it  brings  reproach  on 
opticians  as  a  class. 

A  FIXAL  CASE  OF  IIYPERMETROPIA  IN  WHICH  CONCAVE  GLASSES 
WERE  PRESCRIBED. 

r^lRS.  K.  G.  Aged  twenty-three  years.  Had  been  having 
trouble  with  her  eyes  for  some  time  previously,  and  about  three 
months  ago  consulted  an  optician,  who  gave  her  a  pair  of  — 
I  D.  glasses.  She  has  tried  to  wear  these  glasses,  but  they 
cause  her  eyes  to  ache,  and  she  is  unable  to  thread  a  needle 
^vilh  them.  '  ' 

A  careful  examination  was  made  with  the  following 
result:  R.  E.,  vision  ^f;  with  -f-  i  D.  =  |f.  L.  E.,  vision  = 
If,  with  a  manifest  hypermetropia  of  .75  D.  Is  able  to  read 
Jaeger  No.  4  only,  6  in.  to  11  in.  The  above  lenses  increase 
the  reading  far  point  to  sixteen  inches.  Ordered  R.  E.  +  i, 
L.  E.  +  .75,  for  constant  wear,  and  these  alTorded  the  greatest 
comfort  and  satisfaction. 

MORAL   OF  THESE   CASES. 

The  wTitcr  could  give  the  history  of  a  great  many  more 
similar  cases  from  his  own  case-books,  but  sufficient  have 
probably  been  narrated  to  call  attention  to.  and  to  emphasize, 
this  most  important  point,  that  is.  the  great  danger  to  the  eye 
when  concave  glasses  are  prescribed  in  cases  of  hypermetropia. 
Of  course  it  is  a  natural  error,  into  which  the  optician  may 
easily  be  misled  by  the  patient's  statements  that  he  is  near- 
sighted, and  by  his  answers  when  test  lenses  are  placed  before 
his  eyes;  but  it  is  to  be  hoped  that  no  reader  of  The  ^1  wrAf, 
will  ever  allow  himself  to  fall  into  such  an  error,  and  he  cer- 


HVrERMETROPIA.  41 

-.ainly  will  not  if  he  carefully  follows  the  directions  given  in 
-ihis  chapter  and  in  the  chapter  on  Method  of  Examination. 
Too  much  stress  cannot  be  laid  on  the  importance  of  the 
oroper  differential  diagnosis  between  hypermetropia  and 
myopia,  and  at  the  risk  of  repetition  (which,  after  all,  serves 
as  the  best  means  of  fixing  a  fact  in  the  student's  mind)  we 
will  repeat  the  rule  as  follows:  In  testing  the  refraction  of  an 
-eye  ahavys  commence  icith  convex  lenses,  and  if  these  make 
vision  clearer,  or  if  they  are  accepted  at  all,  it  is  prima  facie 
evidence  of  the  existence  of  hypermetropia;  for  the  diagnosis 
of  hypermetropia,  in  testing  with  the  trial  case,  depends  upon 
-.he  acceptance  of  a  convex  lens  for  distance,  and  in  such  a  case 
concave  lenses  should  not  be  used,  else  they  too  be  accepted, 
-tnd  then  the  optician  becomes  mixed  and  the  diagnosis  is  in 
loubt.  For  it  should  be  remembered  that  weak  concave 
u-lasscs  are  accepted  for  distance  by  almost  every  eye,  and 
rarely  fail  to  cause  some  slight  improvement  in  vision;  and 
nence  if  they  are  tried  first  and  at  once  accepted,  the  optician 
may  too  hastily  jump  to  the  conclusion  that  the  case  is  one 
of  myopia,  and  may  be  led  to  commit  the  unpardonable  error 
of  prescribing  concave  glasses  in  a  case  of  hypermetropia. 

LATKNT    nVPERMETROPIA. 

The  optician  will  sometimes  meet  with  cases  of  suspected 
:iypermetropia  that  will  not  accept  convex  lenses;  their  vision 
is  ^g.  and  all  convex  lenses  blur  it.  In  spite  of  this  all  the 
svmptoms  may  point  to  hypennetropia,  and  the  optician  may 
oc  able  to  detect  its  presence  by  the  retinoscope  and  by  other 
means  which  will  be  described  later  on.  Such  patients  are 
\mable  to  relax  their  long-contracted  ciliary  muscles  in  the 
j-lightest  degree;  and  in  these  cases  the  total  hypermetropia  is 
all  latent.  This  condition  of  non-relaxation  of  the  muscle  of 
accommodation  is  most  frequently  found  in  young  persons, 
:n  whom  it  is  strong  and  vigorous.  In  some  cases  where 
-onvex  lenses  are  thus  rejected  when  each  eye  is  tested 
separately,  it  may  be  possible  to  secure  their  acceptance  by 
'.rying  the  eyes  together  in  binocular  vision,  when  the  accom- 
.modation  relaxes  more  readilv. 


42  IIVPERMETROriA. 


THE   OrilTIIALMOSCOPE   IX    IIvrM-.KM  ETROl'IA. 

It  has  been  stated  that  the  hypermetropic  eye,  when  at 
rest,  is  adapted  for  converg-ent  rays,  and  hence  when  the  eye 
is  strongly  illuminated,  the  emergent  rays  will  follow  the  same 
course  in  returning,  and  as  a  consequence  will  diverge  from 
the  surface  of  the  cornea.  During  the  ophthalmoscopic  ex- 
amination of  the  hypermetropic  eye  by  the  direct  method,  the 
instrument  is  held  very  close  to  the  eye  under  observation, 
and  the  optician  rotates  behind  the  mirror,  and  into  its  aper- 
ture, a  convex  lens  of  sufficient  refractive  power  to  render 
parallel  the  divergent  rays  issuing  from  the  patient's  eye,  when 
an  erect,  virtual,  ma^iified  image  of  the  retina  of  this  eye  will' 
become  visible  to  the  observer.  The  focal  power  of  the  con- 
vex lens  necessary  to  make  the  divergent  rays  parallel  will 
represent  the  degree  of  the  hypermetropia. 

This  method  of  determining  the  refraction  does  not  always 
yield  accurate  results,  and  should  not  be  relied  upon  to  the 
exclusion  of  the  test  by  trial  lenses;  but  in  cases  where  the 
answers  are  unsatisfactory  with  the  trial  case,  and  particularl}^ 
in  children,  it  suffices  to  give  a  very  satisfactory  clue  to  the 
condition  of  the  refraction  and  the  degree  of  defect.  With 
the  improved  ophthalmoscopes  of  the  present  day,  the  proper 
correcting  lens  can  be  found  by  simply  rotating  the  disk  until' 
the  strongest  convex  lens  is  reached  that  does  not  blur  the 
retinal  picture. 

FAR-SIGHTEDXESS. 

The  common  term  in  use  among-  the  lait}-  for  hyper- 
metropia is  "far-sightedness,"  in  contradistinction  to  near- 
sightedness, the  common  name  for  myopia.  As  this  term- 
would  indicate,  the  idea  generally  prevails  that  the  hyper- 
metropic eye  can  see  at  a  greater  distance  and  can  see  better 
far  off  than  an  emmetropic  eye.  This  is  a  great  mistake; 
nothing  can  be  better  for  vision  than  a  normal  or  emmetropic 
eye.  Instead  of  being  more  advantageous,  the  hypermetropic 
eye  is  an  undeveloped  eye,  and  because  of  this  incompleteness 
there  is  apt  to  be  an  insufficiency  in  the  layer  of  rods  and  cones 
of  the  retina,  as  well  as  of  the  optic  nerve  fibers,  and  therefore 


HYPERMETROriA.  4t> 

the  vision  can  scarcely  measure  up  to  the  normal  standard  of 
distinctness  for  distant  objects,  much  less  for  near  ones. 

COURSE  OF  IIVPERMETROriA. 

While  myopia  inclines  to  increase  in  proportion  to  the 
close  use  of  the  eyes  and  in  consequence  thereof,  hyper- 
metropia,  on  the  other  hand,  rarely  increases,  but  rather  tends 
to  decrease.  It  has  been  shown  that  the  hypermetropic  eye 
possesses  a  larger  ciliary  muscle  than  the  myopic  or  the  em- 
metropic eye,  and  that  its  circular  fibers  particularly  are  more 
highly  developed,  few  or  none  of  which  are  found  in  the 
myopic  eye.  The  statement  is  also  made  that  the  yellow  spot 
is  situated  farther  toward  the  temporal  side  than  is  the  case 
in  the  emmetropic  eye,  thus  increasing  the  distance  between 
the  disk  and  the  macula. 

VISION    IN    HYPERMETROPIA. 

In  the  lower  grades  of  hypermetropia  during  adolescence, 
vision  usually  equals  |^,  and  the  defect  is  almost  or  altogether 
latent,  and  is  therefore  difScult  of  detection;  but  in  the  higher 
grades  of  the  defect  vision  is  more  or  less  impaired,  even  wdien 
the  hypermetropia  is  completely  neutralized  by  the  proper 
convex  lenses. 

This  deficiency  of  sight  depends  partly  on  the  insufificiency 
of  the  rods  and  cones  of  the  retina  as  mentioned  above,  but 
more  perhaps  on  the  nearness  of  the  retina  to  the  nodal  point, 
which  causes  the  size  of  the  retinal  images  to  be  smaller  than 
in  emmetropic  eyes,  and  being  smaller  they  are  able  to  impress 
fewer  of  the  perceptive  nervous  elements.  Even  when  the 
size  of  the  images  is  increased  by  the  magnifying  effect  of 
convex  lenses,  the  vision  is  not  always  raised  to  normal,  which 
tends  to  prove  the  scarcity  of  the  rods  and  cones. 

For  these  reasons  persons  with  a  marked  degree  of  hyper- 
metropia cannot  see  well  at  night  or  in  dimly-lighted  rooms. 
Such  persons  fall  into  the  habit  of  partially  closing  their  lids, 
and  bringing  small  objects  well  illuminated  quite  close  to  the 
eyes,  where  for  a  short  time  they  can  be  seen  distinctly.  The 
holding  of  objects  close  to  the  eyes  is  so  contrary  to  the  popu- 


44  HYPERMETROPIA. 

lar  ideas  about  far-sightedness,  that  an  explanation  of  this 
phenomenon  would  not  be  out  of  order.  As  the  object  ap- 
proaches the  eye  the  size  of  the  retinal  image  increases  to  a 
much  greater  extent  than  the  circles  of  diffusion.  The  strong 
illumination  which  is  necessary  to  enable  the  objects  to  be  seen 
causes  a  contraction  of  the  pupil,  which  shuts  out  the  circum- 
ferential rays  and  diminishes  the  diffusion  circles,  in  which  it 
is  aided  by  the  half-closed  lids.  At  the  same  time  the  hyper- 
metrope  leanis  to  suppress  the  impressions  of  any  un-united 
rays  that  fall  upon  the  retina.  In  this  way  these  hyper- 
metropes  are  sometimes  able  to  do  fine  work  and  read  small 
print  even  without  the  aid  of  glasses,  a  fact  that  is  almost  in- 
credible. Is  it  any  wonder  then  that  these  cases  are  sometimes 
confounded  with  myopia?  They  can,  however,  see  distant 
objects  with  convex  g-lasses,  which  would  be  quite  impossible 
in  myopia. 

Tlie  ability  to  read  so  close  to  the  eyes  requires  a  very 
•strong  supply  of  light,  not  only  to  illuminate  the  letters,  but 
also  to  contract  the  pupil  to  its  smallest  size,  which,  assisted 
"by  the  partially  closed  lids,  acts  as  a  stenopaic  apparatus,  very 
much  on  the  same  principle  as  the  improvement  in  vision 
caused  by  the  pin-hole  disk;  we  consider  a  single  ray  as 
emanating  from  each  point  of  an  object,  and  passing  through 
the  dioptric  media  and  forming  an  image  on  the  retina. 

ESTIMATION    OF    THE   TOTAL    HYPERMETROPIA. 

The  total  hypermetropia  can  be  determined  upon  by  par- 
alyzing the  accommodation  by  a  strong  solution  of  atropine 
(or  one  of  the  other  mydriatics)  and  then  selecting  the  glass 
that  affords  the  best  distant  vision.  The  total  hypermetropia 
as  thus  ascertained  is  oftentimes  very  much  greater  than  the 
manifest  error.  The  writer  has  seen  many  cases  where  the 
manifest  hypermetropia  was  less  than  i  D.,  and  some  in  which 
there  was  no  evidence  even  of  any  manifest  defect,  where  he 
found  the  total  h3^permetropia,  as  revealed  by  the  mydriatic, 
to  be  3  D.  or  4  D.  and  even  more. 


HVrERMETROriA.  45 

THE  USE  OF  ATROPINE  DISCOUNTENANCED. 

But  tlie  employment  of  atropine  belong-s  largely  to  the 
province  of  the  physician  or  oculist,  and  we  advise  against 
its  use  by  the  optician.  It  produces  a  most  alarming  disturb- 
ance of  vision  in  hypermetropic  eyes,  which  in  some  cases 
has  so  frightened  the  individual,  even  where  he  was  advised 
in  advance  of  its  probable  effect,  that  he  has  refused  to  submit 
to  a  second  instillation  of  the  drug,  and  either  tried  to  get 
along  without  glasses  or  sought  them  elsewhere. 

Many  persons  liave  consulted  the  writer,  who  have  at- 
tributed (whether  justly  or  unjustly)  much  of  their  trouble  to 
the  atropine  that  had  been  dropped  in  their  eyes,  and  have 
declared  with  the  greatest  positiveness  that  their  sight  has 
never  been  as  good  since  the  drug  was  used,  as  it  had  been 
before.  In  view  of  the  possibility  of  such  an  experience,  it 
would  scarcely  be  policy  for  the  optician  to  run  the  risk  of 
injuring  his  reputation  in  this  way. 

Nor  indeed  is  it  really  necessar)'  in  a  majority  of  cases; 
for  even  though  the  total  hypermetropia  is  ascertained  by  the 
use  of  the  mydriatic,  the  patient  would  be  unable  to  wear 
glasses  strong  enough  to  correct  it  all.  In  fact,  the  custom  of 
the  writer  is  to  advise  his  students  to  correct  only  the  manifest 
error,  and  in  almost  all  cases  it  will  be  found  that  such  glasses 
are  about  as  strong  as  the  patient  can  wear.  This  is  particu- 
larly true  of  young  persons,  in  whom  the  accommodation  is 
strong  and  active.  As  the  person  grows  older,  and  the  ac- 
commodation lessens  and  weakens,  more  and  more  of  the 
latent  defect  becomes  manifest,  and  stronger  and  stronger 
glasses  can  be  borne  and  are  called  for. 

We  repeat  the  statement  that  almost  any  case  of  hyper- 
metropia can  be  corrected  without  the  use  of  atropine,  at  least 
temporarily.  Tlie  ^^Titer  does  not  employ  the  dnig  nearly 
so  much  as  he  did  in  the  earlier  years  of  his  practice.  He  has 
frequently  found  that  the  glasses  that  were  indicated  by  the 
preliminary  examination,  were  the  same  glasses  that  were  pre- 
scribed after  repeated  examinations  under  atropine,  because 
his  experience  had  taught  him  that  the  total  error  could  not 
all  be  neutralized;  and  this  experience  has  occurred  so  often 


AG  IIVrKRMi:TK01'IA. 

that  he  was  led  to  look  upon  atropine  as  ahiiost  superlluous 
in  the  detection  and  correction  of  the  majority  of  cases  of 
optical  defect,  because  the  result  of  a  careful  examination 
Avithout  atropine  indicates  glasses  about  as  strong  as  they 
can  be  borne  even  after  the  use  of  the  drug. 

While  atropine  is  used  and  the  glasses  are  prescribed 
Avhile  the  eyes  are  still  under  its  influence,  such  glasses  usually 
prove  to  be  too  strong,  so  much  so  as  to  prohibit  their  use, 
because  the  attempt  is  made  to  correct  too  much  of  the  latent 
defect.  We  will  cite  a  case  in  illustration,  in  which  there  is 
only  a  slight  manifest  error,  but  probably  a  marked  degree  of 
latent  defect.  Atropine  had  previously  been  used  by  another 
physician,  which  developed  the  latent  hypermetropia  and  the 
glasses  had  been  prescribed  accordingly,  with  the  result,  as 
so  often  happens,  that  they  could  not  be  worn. 

CASE    OF    HYPERMETROPIA    CORRECTED    UNDER    ATROPINE    IN 
WHICH    THE    GLASSES    WERE    NOT    SATISFACTORY. 

J.  L.  B.  Aged  eighteen  years.  Always  had  weak  eyes 
and  has  suffered  a  great  deal  with  neuralgia  in  eyes.  About 
two  years  ago  was  given  a  pair  of  glasses,  which  w^ere  fitted 
after  repeated  examinations  under  atropine,  but  they  have 
never  been  of  any  benefit  to  her,  and  in  fact  she  not  been  able 
to  W'Car  them.  Vision  of  both  eyes  is  j|,  and  she  accepts  +  .25 
C.  axis  90°.  Reads  Jaeger  No.  4,  4^  inches  to  36  inches. 
These  cylinders  were  ordered  for  constant  wear;  they  afforded 
her  the  greatest  satisfaction  and  relieved  all  the  unpleasant 
symptoms  of  which  she  complained. 

There  is  possibly  some  latent  hypermetropia  in  this  case 
m  connection  with  the  slight  hypermetropic  astigmatism,  but 
which  W'Ould  not  bear  correction,  as  evidenced  by  the  trouble 
with  the  glasses  first  prescribed. 

LATENT  HYPERMETROPIA  VS.   MANIFEST. 

In  some  cases  the  hypermetropia  may  be  almost  entirely 
latent,  and  a  casual  examination  would  show  very  little,  if  any, 
■manifest  error.  In  other  cases  the  hypermetropia  may  be 
almost  entirely  manifest,  and  an  examination  under  atropine 
would  reveal  very  little,  if  any,  latent  defect.     Another  point 


IIVPERMETROPIA.  .       47 

Avith  which  the  optician  should  be  famiHar,  is  the  fact  that  the 
amount  of  discomfort  is  not  always  proportionate  to  the  degree 
of  hypermetropia. 

These  points  are  well  illustrated  in  the  two  following- 
cases,  both  of  whom  happened  to  be  under  niy  care  at  the 
same  time: 

A  CASE   IN   WHICH   THE   HYPERMETROriA   IS   ALMOST   ENTIRELY 
MANIFEST. 

Mrs.  J.  M.  H.  Aged  forty-two  years.  About  eight 
years  ago  eyes  first  commenced  to  trouble  her,  but  they  have 
been  getting  worse  during  the  past  two  or  three  years.  Has 
had  her  glasses  changed  frequently,  but  to  no  advantage.  Her 
present  glasses,  which  were  given  her  for  reading  only,  are  -f- 
1.50  D.,  besides  which  she  also  has  a  pair  of  -f  2  D.  Com- 
plains of  frequent  attacks  of  neuralgia.  Unable  to  read  or  sew 
more  than  five  minutes  at  a  time,  when  she  begins  to  feel  sick 
and  dizzy.  V.  =  ^^  ;  Hm.  =  +  2.50  D.,  with  which  V.  =  -j  5. 
Can't  see  to  read  without  glasses;  with  +  3.50  D.  reads  Jaeger 
Xo.  4,  8  to  32  inches. 

.Under  atropine,  V.  =i5tjV.    Ht.  =  -f  3.50  D.  with  which 

Ordered  -f  2.50  D.  for  distance,  and  -f  4  D.'  for  reading. 
These  glasses  relieved  the  neuralgia  and  enabled  her  to  use  her 
eyes  with  comfort. 

The  optician  who  fitted  this  case  with  -f  2  D.  for  reading 
evidently  did  not  or  could  not  test  her  refraction  to  determine 
if  she  was  hypermetropic  or  if  any  other  error  existed  He 
mistook  it  for  a  case  of  early  presbyopia,  and  as  she  was  not 
very  far  advanced  in  years,  he  was  afraid  of  giving  her  glasses 
too  strong;  they  were  not  sufficient  to  correct  the  manifest 
hypermetropia,  much  less  to  enable  her  to  read  or  sew  with 
any  degree  of  comfort. 

A   CASE   IN   WHICH   THE   HYPERMETROPIA   IS  ALMOST   ENTIRELY 
LATENT. 

Mrs.  Dr.  G.  A.  K.  Aged  thirty-one  years.  Has  been 
wearing  glasses  more  or  less  for  reading  and  sewing  for  the 
past  eleven  years.  Her  reading  glasses  are  -f  1.50  D.,  which 
she  uses  without  much  discomfort.     Her  eves  trouble  her  most 


48  IIYrKRMETROriA. 

when   from   any  cause  her  system   is   run   down,   while   ih 
annoy  her  but  little  when  she  enjoys  her  usual  health.     Slvr 
has  no  particular  difficulty  with  her  eyes  at  present,  but  h   - 
luisband,  being-  a  physician,  advises  her  to  have  her  eye;  c  , 
amined. 

V.  =  If.  Hm.  =  +  .75  D.  Reads  Jaeger  No.  3.  11  ::. 
to  30  in.  Under  atropine  V.  =  ijVV-  Ht.  =  +  4  D.,  \vir,b 
which  V.  =  xF-  Ordered  +  2.50  D.  for  reading,  but  she  com- 
plained that  these  were  too  strong,  and  not  entirely  comforr.- 
able  in  spite  of  the  degree  of  hypermetropia  present,  and  I  wa.^ 
compelled  to  reduce  them  to  -!-  1.50  D.  for  reading,  the  same 
number  she  had  been  using.  As  her  distant  vision  was  unim- 
paired, and  she  had  no  trouble  with  her  eyes,  glasses  for  con- 
stant wear  seemed  unnecessary. 

THESE   CASES   COMPARED. 

A  careful  study  and  comparison  of  these  two  cases  will 
amply  repay  the  practical  optician,  and  to  assist  him  we  will 
make  mention  of  a  few  of  the  important  points.  In  the  first 
place,  Mrs.  H.,  with  a  total  hypennetropia  of  3.50,  sufifers 
greatly  with  neuralgia  and  inability  to  use  her  eyes,  while  Mrs. 
K.,  Adth  a  total  error  of  4  D.,  has  no  pain  and  uses  her  eyes 
with  comparative  comfort. 

In  the  next  place,  Mrs.  H.  shows  a  manifest  defect  of  2.50 
D.,  while  Mrs.  K.,  whose  total  defect  is  .50  D.  greater  than 
Mrs.  H.,  reveals  a  manifest  error  of  only  .75  D,  This  ac- 
counts for  the  difference  in  the  glasses  prescribed  for  each  lady, 
and  explains  why  Mrs.  K.  needs  no  glasses  for  distance,  and 
why  such  weak  glasses  suffice  for  her  for  reading.  Of  course 
the  difference  in  the  age  of  these  patients  is  the  reason  for  the 
variance  in  the  symptoms  referred  to.  In  the  first  case  the 
accommodation  is  weakened  by  age  and  is  unable  to  overcome 
the  defect,  and  in  the  second  case  it  still  retains  the  vigor  of 
youth  and  suffices  to  keep  the  refractive  power  of  the  eye  up  to 
the  necessary  degree. 

HISTORY  OF  HYPERMETROPIA. 

The  slighter  degrees  of  hypermetropia  occasion  but  little 
inconvenience  until  the  individual  reaches  the  thirties,  when 


HYPERMETROPIA.  49 

it  manifests  itself  ciiiefly  as  an  early  presbyopia.  In  cases 
where  the  defect  is  a  little  more  marked  (from  i  D.  to  3  D.), 
it  usually  causes  the  condition  of  convergent  strabismus.  In 
still  higher  degrees  of  hypermetropia,  strabismus  may  be 
absent,  but  a  group  of  symptoms  known  as  "asthenopia"  ma\- 
be  produced.  This  is  a  pen  picture  of  the  effects  of  the  several 
degrees  of  hypermetropia,  varying  in  different  cases  according 
to  the  peculiarities  of  each  individual  (his  muscular  power  and 
nervous  susceptibility),  iSometimes  a  very  slight  degree  of 
hypermetropia  may  be  the  cause  of  much  distress;  in  other 
cases  a  much  higher  amount  of  refractive  error  produces  but 
little  discomfort. 

The  asthenopic  symptoms  of  hypermetropia  are  especially 
liable  to  manifest  themselves  after  an  illness,  or  if  the  health 
of  the  patient  is  impaired  from  overwork,  anxiety  or  other 
causes. 

Distant  objects  arc  seen  by  the  cnnnctropic  eye  without 
any  effort  of  accommodation,  consequently  its  whole  power 
is  free  for  use  in  near  vision.  But  in  hypermetropia,  on  the 
contrary,  there  is  no  distinct  vision  of  any  object  even  at  a 
distance,  without  more  or  less  effort  of  acconmiodation. 
Hence  there  is  a  deficiency  of  acconmiodation  to  start  with, 
or  in  other  words  an  extra  weight  to  carry,  and  as  a  matter 
of  course  under  such  circumstances  the  accommodation  gives 
out  much  sooner  than  it  othenvise  would.  The  less  the  degree 
of  hypermetropia,  all  other  things  being  equal,  the  longer  the 
eyes  can  be  used  before  the  annoying  symptoms  supervene. 
Therefore  it  becomes  evident  that  the  length  of  time  the  ten- 
sion of  the  accommodation  can  be  kept  up  is  to  a  great  extent 
dependent  upon  the  degree  of  defect,  or  the  amount  of  extra 
weight  the  ciliary  muscle  has  to  carry. 

In  the  earlier  years  the  soft  and  }iel(ling  crystalline  lens 
and  the  strong  and  well-developed  ciliary  muscle  enable  the 
eyes  to  do  their  work  without  much  complaint  even  in  the 
face  of  a  high  degree  of  hypermetropia.  But  as  years  pass  on 
and  the  lens  becomes  firmer  and  the  muscles  weaker,  then  the 
troublesome  symptoms  manifest  themselves  and  become  very 
aimoying. 


50 


in  ri;K.\ii- iHoiMA  i  .\   en  i  i.orkx. 

'Ilu-  f\c  strain  that  is  caused  by  hypernictropia  cannot 
fail  to  have  an  effect  upon  the  character  and  natural  disposi- 
tion of  children,  and  freciuently  tends  to  render  them  peevish 
and  fretful,  as  well  as  Tlesponding  and  lacking  in  self-reliance. 
The  constant  effort  required  for  vision  retards  the  quickness 
of  perception  and  comprehension,  and  the  exhaustion  that 
is  sure  to  follow  this  continued  straining-  of  the  eyes  interferes 
with  the  concentration  of  the  attention;  for  these  reasons  the 
child  unconsciously  and  without  knowing  the  reason  why, 
acquires  a  distaste  for  l)ooks. 

An  hypermetropic  boy  sits  down  to  study  his  lessons  full 
of  the  enthusiasm  of  youth  and  with  a  determination  to  per- 
form his  task.  Sooner  or  later  a  feeling  of  uneasiness  creeps 
over  him  and  makes  him  restless.  He  thinks  he  needs  more 
light  and  he  moves  near  to  the  window  or  close  to  the  lamp. 
Then  the  glare  of  the  increased  light  irritates  the  eyes,  and 
they  begin  to  feel  heavy,  and  the  face  becomes  flushed.  He 
makes  effort  after  effort  to  continue  his  work,  but  he  finds 
it  is  of  no  use;  his  head  droops  over  the  table,  and  he  finally 
falls  asleep. 

This  struggle  is  repeated  day  after  day,  and  the  naturally 
bright  boy  becomes  backward  and  stupid.  He  gradually  loses 
his  desire  for  study,  and  he  continues  through  life  without  the 
habit  of  application  and  the  power  of  concentration,  which  are 
so  essential  to  success,  and  all  on  account  of  a  neglected  optical 
defect,  which  should  have  been  corrected  at  the  commence- 
ment of  his  education. 

])ETKRMIXATIOX    OF    II VPERMETROPIA. 

The  optician  will  be  able  to  determine  the  existence  of 
hypermetropia  when  any  one  of  the  following  conditions  is 
found  to  be  present : 

1.  When  distant  vision  is  improved  by  a  convex  lens,  or 
when  the  acuteness  of  vision  equals  |;;  and  is  just  as  good 
with  a  convex  lens  as  without. 

2.  When  a  patient  is  able  to  read  fine  print  through  a 
convex  glass  at  a  greater  distance  than  the  focal  length  of 
the  lens. 


ve  V 
off 


HVl'ERMETROPIA.  51 

3,  When  the  near  point  hes  at  a  greater  distance  from 
the  eye  than  is  proper  for  the  age,  or  when  the  amphtude  of 
accommodatioii  falls  below  the  normal  standard.  A  refer- 
ence to  the  tables  in  the  Chapter  on  Presbyopia  will  show 
the  distance  of  the  near  point  and  the  amount  of  amplitude  of 
accommodation  at  the  various  ages,  a  departure  from  which 
can  be  readily  detected. 

4.  When  with  the  ophthalmoscope  the  fundus  of  the  ey 
can  be  distinctly  seen  with  a  convex  lens  in  the  aperture 
the  instrument.  ^ 

The  presence  of  any  or  all  of  these  conditions  indicates  / 
The  existence  of  hypermetropia,  which  is  then  to  be  measured 
rind  corrected  by  the  means  to  be  described. 

AMOUNT   OF   HVrERMETROPIA. 

The  amount  of  hypermetropia  may  vary  from  a  fraction 
of  a  dioptric  to  fifteen  dioptrics;  when  it  exceeds  6  D.  it  is 
looked  upon  as  a  case  of  high  hypermetropia.  W'hen  the 
defect  is  under  4  D.  in  young  persons  with  a  good  accom- 
modation, the  acuteness  of  vision  as  a  rule  is  normal  and 
equals  |y.  Such  patients  may  accept  weak  convex  lenses, 
but  without  any  improvement  in  vision,  which  has  not  fallen 
below^  the  normal  standard,  the  defect  existing  in  the  latent 
form.  When  the  degree  of  hypermetropia  is  greater  than  4 
D.,  the  vision  is  apt  to  be  more  or  less  impaired,  which  in 
moderate  degrees  is  raised  to  normal  by  the  proper  convex 
lenses.  In  extreme  cases  of  high  hypermetropia  it  is  impos- 
sible to  secure  normal  vision  by  the  most  carefully  adjusted 
glasses. 

SIGNS    OF   HYPERMETROPIA. 

The  presence  of  hypermetropia  makes  it  a  matter  of  more 
or  less  difficulty  to  maintain  distinct  vision  of  small  objects 
for  any  great  length  of  time.  The  vision  begins  to  blur  and 
the  patient  is  compelled  to  stop  reading  and  rub  his  eyes. 
This  for  the  moment  seems  to  clear  up  the  vision,  and  the 
lxx)k  is  again  taken  up  and  a  fresh  start  is  made;  but  the 
blurring  occurs  again  and  again  until  finally  the  accommoda- 
tion becomes  entirely  exhausted,  and  the  reading  must  be 
discontinued. 


52  lIVrERMETROriA. 

The  book  is  often  held  in  a  very  strong  Hght,  which  serves 
to  contract  the  pupil  and  thus  render  vision  clearer.  At  the 
same  time  many  hypermetropic  persons  fall  into  the  habit  of 
holding  the  book  quite  close  to  their  eyes,  thus  increasing  the 
size  of  the  visual  angle,  when  vision  is  also  assisted  by  the 
half-closed  lids  acting  as  a  stenopaic  apparatus. 

PAIN    IN    HYPERMETROPIA, 

One  of  the  principal  subjective  symptoms  of  which  the 
hypermetropic  patient  complains  is  pain,  which  varies  very 
much  as  to  its  character  and  location.  Sometimes  it  is  in  the 
eye-ball,  sometimes  over  the  brow  and  through  the  temple, 
sometimes  on  the  top  of  the  head,  sometimes  in  the  back  of 
the  head  and  nape  of  the  neck,  and  in  extreme  cases  the  pain 
may  be  accompanied  by  nausea  and  vomiting.  Headache  is  a 
very  common  symptom,  and  is  often  described  under  the 
French  term  migraine. 

TESTING   HYPERMETROPIA. 

If  the  symptoms  have  indicated  the  existence  of  hyper- 
metropia,  and  the  preliminary  examination  has  confirmed  this. 
the  eyes  must  then  be  carefully  tested  to  determine  the  degree 
of  defect.  Each  eye  should  be  tested  separately,  noting  first 
its  visual  acuteness,  and  then  commencing  the  test  with  weak 
convex  lenses. 

If  a  mild  convex  glass  is  accepted,  the  diagnosis  of  hyper- 
metropia  is  assured,  and  then  stronger  and  stronger  glasses 
are  placed  before  the  eye  in  rapid  succession,  until  the 
strongest  convex  lens  is  reached  with  which  the  patient  is  able 
to  read  |^  ;  or  if  it  is  impossible  to  raise  the  acuteness  of  vision 
to  normal,  then  the  strongest  convex  lens  that  affords  the  best 
sight  in  looking  at  the  card  hanging  twenty  feet  away.  Tliis 
is  the  measure  of  the  manifest  hypermeiropia. 

If  the  acuity  of  vision  is  not  raised  to  normal  by  a 
convex  spherical  lens,  there  is  a  possibility  of  the  existence 
of  an  astigmatic  element  in  the  case,  for  which  a  careful  ex- 
amination should  be  made.  If,  however,  vision  equals  |^ 
with  the  spherical  lens,  it  is  hardly  likely  that  any  astig- 
matism is  present,  but  still  every  case  should  be  tested  with 


IIYPERMETROPIxV.  53 

a  view  of  its  detection  if  it  exists.  If  none  is  present,  the  con- 
vex lens  is  all  that  is  necessary  to  correct  the  ametropia.  In 
order  to  insure  accuracy,  this  examination  should  be  repeated 
two  or  three  times  on  as  many  different  days. 

In  cases  where  vision  is  found  to  be  exactly  alike  in  the 
two  eyes,  and  if  spasm  of  the  accommodation  is  suspected, 
the  two  eyes  may  be  tested  together,  when  more  suitable 
glasses  can  oftentimes  be  obtained  in  this  way  by  the  accept- 
ance of  stronger  glasses,  than  when  one  eye  is  excluded  from 
the  act  of  vision,  because  with  parallel  axes  the  accommoda- 
tion is  more  apt  to  relax. 

THE    METHOD    BY    OVER-CORRECTIOX. 

In  cases  where  the  hypermetropia  exists  largely  in  a  latent 
form,  and  where  there  is  consequently  difficulty  in  having  the 
patient  accept  convex  lenses,  the  following  "method  by  over- 
correction" will  often  yield  satisfactory  results. 

Place  in  the  trial  frame  a  stronger  convex  lens  than  is  re- 
quired, that  is,  one  strong  enough  to  greatly  over-correct  the 
defect.  This,  of  course,  blurs  the  vision,  but  at  the  same  time 
it  encourages  the  accommodation  tO'  relax,  as  the  more  the 
relaxation  of  the  accommodation  the  greater  the  improve- 
ment in  vision. 

Then  place  in  the  trial  frame,  in  front  ot  this  convex  lens, 
a  weak  concave  lens,  which  at  once  causes  an  improvement  in 
vision.  Then  try  successively  stronger  and  stronger  concave 
lenses  until  the' zvcakcst  one  is  found  that  affords  a  vision  of 
^g,  and  then  the  difference  between  the  two  lenses  will  be 
the  measure  of  the  manifest  hypermetropia. 

F'or  instance,  a  -|-  6  D.  lens  is  placed  in  the  trial  frame, 
Mith  which  perhaps  vision  is  only  equal  to  ^%%.  Concave 
lenses  improve  this  vision,  and  it  is  found  a  —  4  D.  enables 
the  patient  to  read  |§,  in  which  case  -f  2  D.  is  the  measure 
•of  the  manifest  hypermetropia. 

LATENT    HYPERMETROPIA    BECOMES    MANIFEST. 

As  age  advances  and  the  vigor  of  accommodation  lessens, 
If  there  is  any  latent  hypermetropia  it  gradually  becomes 
manifest.    A  person  may  have  6  D.  of  latent  hypermetropia  at 


54  IIYrF-RMHTKOl'IA. 

ten  years  of  age,  when  the  defect  is  (Hfficult  of  detection,  or 
perhaps  its  existence  may  not  even  he  suspected.  At  thirty- 
five  years  of  age  half  of  it  (3  D.)  may  have  become  manifest 
and  is  easily  discovered  by  the  usual  tests,  and  after  middle 
age  the  whole  of  it  becomes  manifest  and  complicates  and 
augments  the  natural  condition  of  presbyopia,  and  then  the 
total  hypermetropia  and  the  manifest  hypcrmctropia  are 
synonymous  terms. 

A  IIVrERMETROPlC  EYE  CIIANGIXG  ITS  REFRACTION. 

The  normal  condition  of  refraction  in  childhood  is  one 
of  hypermetropia,  as  has  been  stated;  some  persons  retain  this 
condition  all  through  life,  a  considerable  number  become  em- 
metropic as  they  grow  older,  while  a  certain  percentage  pass- 
over  into  a  condition  of  myopia.  In  all  these  changes,  from 
hypermetropia  to  emmetropia  and  from  emmetropia  to 
myopia,  there  is  a  gradual  lengthening  in  the  antero-posterior 
diameter  of  the  eye-ball,  and  the  rapidity  of  the  changes  and 
the  degree  of  myopia  finally  attained  will  depend  on  the 
amount  of  lengthening  and  the  recession  of  the  retina  from 
the  focus  of  the  parallel  rays. 

When  these  changes  occur  they  usually  take  place  before 
adult  age  is  reached.  In  childhood  and  youth  the  membranes 
and  tissues  of  the  eye  are  soft  and  yielding,  and  can  offer  but 
little  resistance  to  the  causes  that  tend  to  elongate  the  ball. 
After  twenty  years  of  age  the  tunics  of  the  eye,  and  especially 
the  sclerotic,  become  tough  and  firm,  after  which  there  is  little 
danger  of  these  morbid  changes  taking  place,  or  if  they  have 
already  commenced,  their  progress  is  now  checked. 

SPASM    OF    ACCOM.MODATIOX. 

On  account  of  the  persistent  contraction  of  the  ciliary 
muscle  which  is  necessary  to  overcome  the  error  of  refraction 
and  render  vision  distinct,  hypermetropia  often  gives  rise  to 
a  condition  which  has  been  termed  spasm  of  the  accommodation. 
This  simulates  myopia  in  all  of  its  symptoms,  the  resemblance 
being-  particularly  noticeable  in  the  impairment  of  distant 
vision  and  the  confirmed  habit  of  holding  the  book  close  to 
the  eyes.     In  these  cases  concave  lenses  are  often  accepted 


IIVPEKMKTKOPJA.  ■):> 

and  may  cause  a  great  inipravenK'nt  in  distant  vision ;  but 
it  need  hardly  be  said  that  no  well-informed  optician  would 
order  them,  as  they  would  only  aggravate  the  trouble  and 
impose  a  greater  strain  on  the  accommodation. 

This  state  of  spasm  is  apt  to  occur  in  persons  whose  ner\  - 
ous  system  is  in  a  low  state  of  vitality,  and,  strange  to  say,  ii 
seems  to  bear  no  relation  to  the  vigor  of  the  accommodation. 
It  is  almost  incredible  that  persons  W'ith  a  weak  accommoda- 
tion should  sufifer  with  constant  contraction  of  the  ciliary  mus- 
cle; but  such  is  really  the  case.  It  might  be  well  to  remark 
in  passing  that  spasm  of  accommodation  ma\'  occur  in  crm- 
ditions  of  refraction  other  than  hypermetropia. 

TRK.\TMi:X'r    OF    IIYPKK.METKOPIA. 

]n  absolute  hypermetr(.)pia  vision  is  indistinct  at  all  dis- 
tances. The  accommodation  is  not  equal  to  the  task  of  unit- 
ing even  parallel  rays  (those  from  a  distance)  in  a  focus  oti 
the  retina,  much  less  divergent  rays  (those  from  near  objects). 
In  such  cases  the  rays  must  be  rendered  convergent  beforc 
they  enter  the  eye;  and  this  changing  of  parallel  and  diverging 
rays  into  a  convergent  form  is  accomplished  by  means  of  con- 
vex lenses. 

The  treatment,  then,  of  hypermetropia  consists  in  the 
application  of  a  convex  lens  of  such  strength  as  will  impart 
to  parallel  rays  sufificient  convergence  to  make  them  focus 
upon  the  retina  without  any  effort  of  the  acconmiodation. 


Diagram  of  a  passive  liyperinetr<^)lc  eye,  the  focus  of  parallel 
rays  lying  behind  the  retina,  as  shown  by  the  dotted  lines.  A 
eonvex  lens  plneed  in  front  of  the  eye  converges  the  vays  to  a 
focus  on  the  retina,  as  shown  by  the  plain  lines,  the  accomnio 
datlon  all  the  whil"  bfiiiR  qiiioscMit. 


^>C)  lIVPKRMKTkOriA. 

TWO    PAIRS   OF  GLASSES   MAY   BE   REQUIRED. 

]n  many  cases  two  pairs  of  glasses  may  be  required:  one 
pair  to  enable  distant  objects  to  be  distinctly  seen,  and  another 
pair  to  permit  of  fine  print  being  easily  read  at  the  ordinary 
reading  distance.  Two  pairs  of  glasses  become  a  necessity 
under  one  of  two  conditions:  in  high  degrees  of  hyperme- 
tropia  and  in  hypermetropia  complicated  with  presbyopia. 

When  the  range  of  accommodation  is  much  diminished, 
this  deficiency  may  be  compensated  for  by  a  change  in  the 
position  of  the  glasses.  If  very  strong  convex  glasses  are 
worn,  a  slight  alteration  in  their  distance  from  the  eyes  is 
equivalent  to  a  change  for  those  of  a  greater  or  lesser  power, 
as  may  be  needed  to  make  objects  distinctly  seen  at  diflferent 
distances,  thus  supplementing  the  use  of  the  accommodation 
and  obviating  the  necessity  for  glasses  of  an  intermediate 
focus.  Therefore  great  care  should  be  taken  to  see  that  such 
glasses  are  properly  adjusted  and  centered.  As  these  glasses 
are  usually  required  for  near  vision,  where  a  marked  converg- 
ence of  the  visual  axes  is  called  for,  the  centers  of  the  lenses 
should  be  slightly  approximated,  so  that  the  visual  lines  may 
pass  through  them.  If  this  precaution  be  overlooked  and  the 
rays  of  light  pass  through  the  peripheral  portions  of  the  lenses, 
their  prismatic  effect  is  called  into  play,  which  may  cause  a 
disturbance  of  the  close  relation  which  should  exist  between 
the  functions  of  accommodation  and  convergence,  and  this 
may  be  followed  by  a  train  of  symptoms  making  up  the  con- 
dition of  asthenopia. 

In  facultative  hypermetropia  where  both  near  and  distant 
vision  is  good,  and  the  use  of  the  accommodation  can  be 
continued  without  fatigue  almost  as  long  as  may  be  desired, 
no  glasses  are  necessary  until  the  near  point  has  receded  be- 
yond eight  or  nine  inches.  This  occurs  much  earlier  than  in 
the  normal  eye,  and  such  persons  are  required  to  wear  glasses 
for  close  work  in  many  cases  when  only  twenty-five  or  thirty 
years  old. 

AN  UNNATURAL  USE  OF  THE  ACCOMMODATIOX. 

In  hypermetropia,  as  has  already  been  shown,  either  on 
account  of  the  faultv  formation  of  the  eve-ball  or  of  a  de- 


HYPERMETROPIA.  57 

iiciency  of  refractive  and  accommodative  power,  an  excessive 
iimount  of  muscular  power  is  required  to  adjust  the  dioptric 
^iipparatus  of  the  eye  for  near  vision.  Now,  the  placing  of  a 
•convex  lens  before  such  an  eye  does  away  with  the  necessity 
for  a  certain  amount  of  muscular  effort,  and,  therefore,  the 
lens  represents,  or  is  equivalent  to,  the  expenditure  of  a  cer- 
tain amount  of  muscular  force.  In  other  words,  the  convex 
]ens  lifts  a  load  from  the  shoulders  of  the  overburdened  mus- 
cle, which  is  then  called  upon  to  perform  only  its  legitimate 
Avork. 

In  hypermetropia  the  brain  abhors  the  circles  of  diffusion 
that  would  naturally  be  formed  on  the  retina  and  the  blurred 
vision  that  would  result  therefrom,  and  instinctively  turns  to 
the  function  of  accommodation  and  appeals  to  it  to  bring  the 
focus  of  rays  forward  to  the  retina  and  thus  restore  clearness 
of  vision. 

In  giving  the  hint  to  the  nerve  centers  that  control  the 
accommodation  as  to  what  is  expected  of  it,  and  while  notify- 
ing- it  when  the  time  arrives  for  action,  the  brain  despatches 
sufficient  nerve  force  (no  more  and  no  less)  to  the  ciliary 
muscle  to  accomplish  the  purpose  of  clear  vision.  The  most 
Avonderful  thing  about  this  w'hole  matter  is  the  accuracy  with 
Avhich  the  brain  measures  the  work  that  is  to  be  accomplished, 
•and  the  nicety  with  which  it  sends  forth  just  the  amount  of 
force  required. 

This  is  an  unjust  use  to  which  the  accommodation  is  put, 
Imt  it  must  be  continued  until  the  necessary  glasses  are  sup- 
plied. Transgression  on  any  of  Nature's  laws  is  sure  to  be 
followed  by  punishment  sooner  or  later,  and  the  breaking  of 
this  law  proves  no  exception  to  the  rule,  as  is  shown  by  the  j 
torture  w^hich  some  of  these  hypermetropic  and  asthenopic  y' 
patients  are  compelled  to  sufTer. 

WHAT  GLASSES  TO  PRESCRIBE. 

In  the  correction  of  hypermetropia  by  convex  lenses  in 
the  light  of  the  above  statements,  the  important  question 
naturally  arises  as  to  what  shall  be  the  power  of  the  glass  re- 
quired in  each  individual  case?  This  brings  up  the  subject 
■'>f  the  total  amoinit  of  error,  and  what  proportitm  of  the  latent 


58  lIVrKKMKTRorjA. 

portion  it  is  advisable  to  attempt  to  correct.  Tlie  total  hyper- 
nietropia  is  made  up  of  the  sum  of  the  manifest  and  the  latent^ 
the  divisions  between  which  are  plainly  marked. 

The  former  can  be  easily  measured,  but  the  latter  can  be 
detected  only  by  the  employment  of  atropine,  the  use  of  whichi 
by  the  optician  has  been  discountenanced  on  these  pages  on 
every  occasion.  But,  for  the  sake  of  argument,  suppose  the 
drug  had  been  used  and  the  total  error  determined  in  this  way. 
Theoretically  it  would  seem  to  be  the  proper  thing  to  at  once 
and  completely  neutralize  it,  but  practically  such  glasses  are 
found  to  be  much  too  strong. 

Previously  there  had  been  an  excessive  and  imnaturai 
contraction  of  the  ciliary  muscle,  by  means  of  which  a  por- 
tion of  the  defect  had  been  rendered  latent.  When  the  total 
neutralizing  glasses  are  placed  before  the  eyes,  the  muscle 
should  completely  relax  and  allow  the  defect,  which  it  had 
rendered  latent,  to  now  become  manifest  and  correctible  by 
glasses;  but  instead  of  this,  the  contraction  of  the  muscle  still 
continues,  which,  with  the  action  of  the  convex  lens,  supplies 
an  excess  of  refractive  power,  which  may  result  in  an  aggrava- 
tion of  the  very  symptoms  it  was  intended  to  relieve.  Hence 
the  rule  has  been  formulated  not  to  attempt  to  correct  the  total 
amount  of  hypermetropia  at  the  first  fitting  of  glasses. 


CORRECTION   OF  TOTAL  HYrERMETROriA. 

When  a  hypermetropic  eye  is  under  the  influence  of 
atropine,  vision  at  all  distances  is  blurred  and  indistinct.  Tlie 
full  correction  of  the  defect  is  necessary  to  clear  up  distant 
vision,  and  a  lens  4  D.  or  5  D.  stronger  will  enable  the  patient 
to  see  at  reading  distance.  As  soon  as  the  effects  of  the  drug 
have  worn  off  (which  may  not  be  for  a  week)  and  the  accom- 
modation is  again  allowed  to  exercise  its  function,  then  dis- 
tant vision  is  dimmed  when  the  same  glasses  are  placed  before 
the  eyes,  and  this  haziness,  which  envelopes  all  distant  objects,, 
continues  until  the  glasses  are  taken  ofif.  The  tension  of  the 
accommodation,  which  is  the  disturbing  feature  in  this  prob- 
lem, is  a  variable  quantity  in  different  individuals,  some  few 
persons  bearing  almost  or  quite  the  full  correction  with  little 


HYPERMETROPIA.  5?* 

discomfort,  while  a  great  many  otlicrs  will  tolerate  but  a  small 
part  of  the  correction. 

Oculists  who  are  accustomed  to  employ  atropine  in  the 
correction  of  hypermetropia,  use  different  methods  in  dealing 
with  this  difficulty.  Sometimes  the  full  correction  is  ordered 
and  placed  before  the  eyes  while  still  under  the  influence  of 
the  mydriatic,  and  the  patient  is  instructed  to  wear  them  con- 
stantly all  the  while  that  the  influence  of  the  drug  is  wearing 
off  and  the  accommodation  is  returning  to  its  normal  state. 
In  this  way  it  is  hoped  to  coax  the  eyes  to  accept  the  glasses. 

It  might  be  well  at  this  point  to  remind  the  optician  that 
when  the  glasses  are  fitted  at  fifteen  feet  (and  even  at  twent\" 
feet),  there  is  really  an  over-correction  of  about  .25  D..  because 
the  rays  proceeding  from  these  distances  are  not  strictly 
parallel,  and  hence  the  lens  that  is  required  to  focus  them  per- 
fectly on  the  retina  is  a  little  too  strong  to  exactly  focus 
parallel  rays.  Therefore,  even  when  it  is  desired  to  order  a 
full  correction,  the  glass  which  affords  the  best  vision  under 
atropine  at  fifteen  or  twenty  feet  should  be  weakened  by  .25 
D.  This  is  a  slight  step  in  the  direction  of  enabling  patients 
to  wear  a  full  correction. 

THE  FULL  CORRECTION'  ^L\V  NEED  TO  BE  REDUCED. 

In  Other  cases  the  oculist  may  employ  a  different  mctho<l- 
as  follows :  the  effect  of  the  atropine  is  allowed  to  wear  off  and 
the  eyes  regain  their  full  power  of  accommodation,  after  which 
an  interval  of  one  or  two  weeks  is  permitted  to  pass  before  the 
eyes  are  given  their  final  trial  for  the  glasses  which  are  to  be 
prescribed. 

The  full  correction  as  found  by  the  a,tropine  is  then  placeil 
before  the  eyes,  and  the  effect  on  the  distant  letters  is  noted. 
If  they  afford  a  normal  acuteness  of  vision  (which  unfortu- 
nately is  rarely  the  case)  the  oculist  would  be  justified  in  order 
ing  them.  If,  however,  as  is  usually  the  case,  the  acutenes^ 
of  vision  is  impaired  by  these  full  strength  glasses,  they  arc 
gradually  reduced  little  by  little  until  the  lens  is  arrived  at 
that  permits  a  vision  of  ^^ .  This  may  require  a  reduction  of 
one-fourth,  one-third,  or  even  one-half  of  the  full  amount,  and 
these  weakened  glasses  are  the  ones  that  are  then  ordered. 


€0  HYPERMETROPIA, 


WHY  THEN   USE  ATROPINE? 

This  practically  amounts  to  a  correction  of  the  manifest 
hypermetropia  only,  and  now  the  question  naturally  arises;' 
"Of  what  benefit  is  the  use  of  atropine  to  determine  the  to'tal' 
■error  (which  will  not  bear  neutralization),  when  only  the 
manifest  defect  is  after  all  corrected,  the  amount  of  which  can 
be  just  as  well  determined  without  the  use  of  the  mydriatic?" 
This  question  carries  its  own  answer. 

Exophoria  may  act  as  a  frequent  cause  of  the  inability 
to  wear  the  full  correction  of  convex  glasses  in  hypermetropia, 
•on  account  of  its  accompanying  insufficiency  of  the  internal 
recti  muscles.  In  this  condition  an  extra'  supply  of  nervous 
iorce  is  required  by  these  muscles  in  order  to  maintain  paral- 
lelism of  the  visual  axes,  which  implies  a  corresponding  stimu- 
lation of  the  muscle  of  accommodation.  It  therefore  follows 
that  in  the  face  of  this  constant  incentive  to  action  on  the  part 
-of  the  accommodation,  it  can  hardly  be  expected  to  relax  to 
•any  appreciable  extent  to  admit  of  the  acceptance  of  a  convex 
lens.  A  displacement  of  the  optical  centers  of  these  glasses 
inward  may  be  of  some  benefit,  as  this  will  assist  the  over- 
taxed convergence,  and  in  like  manner  will  tend  to  diminish 
the  accommodation. 

A    PRACTICAL   ILLUSTRATION. 

The  writer  of  these  lines  has  seen  many  cases  of  hyper- 
metropia coming  from  the  hospitals  and  dispensaries  of  this 
city  who  were  unable  to  wear  the  glasses  given  them.  The 
rule  in  these  institutions  is  to  use  atropine  and  correct  the 
"total  error,  the  refracting  being  done  by  assistants  and  begin- 
ners. If  the  patient  returns  with  any  complaint,  he  is  assured 
the  glasses  are  made  according  to  the  prescription,  and  that 
"the  latter  is  correct,  and  he  is  advised  to  persevere  in  their  use. ' 
If  the  luckless  patient  ventures  tO'  return  again  to  find  further 
fault  with  the  glasses,  he  is  given  the  scant  courtesy  that  is  so 
common  in  charitable  institutions,  and  is  dismissed  with  the  • 
statement  that  nothing  more  can  be  done  for  him. 

He  finally  drifts  into  the  office  of  some  oculist  or  falls  into ' 
the  hands  of  some  optician,  who  hears  his  story  and  quickly 


IIVPERMETROPIA.  61 

perceives  the  cause  of  his  trouble,  and,  by  reducing  the 
strength  of  his  glasses,  gives  him  immediate  comfort.  Tliis 
is  a  very  common  occurrence,  and  hence  we  feel  safe  in  making 
the  statement  that  the  optician,  in  the  great  majority  of  cases, 
if  he  exercises  the  proper  care,  will  be  able  to  fit  his  cases 
of  hypermetropia  as  satisfactorily  as  the  oculist  who  uses 
atropine.  Therefore,  the  practical  optician  will  have  to  do 
only  with  the  manifest  hypermetropia,  which  he  is  able  to 
measure  and  correct  by  the  methods  set  forth  in  this  chapter. 
After  the  glasses  have  been  worn  for  awhile,  some  addi- 
tional portion  of  the  latent  hypermetropia  becomes  manifest, 
when  the  glasses  may  be  advantageously  changed  for  those  a 
little  stronger.  After  a  time  another  change  may  be  made  in 
the  same  way,  and  finally  in  some  cases  the  latent  error  be- 
comes almost  or  entirely  manifest,  when  glasses  corresponding 
to  the  degree  of  the  total  hypermetropia  are  the  proper  ones 
to  prescribe,  and  no  further  changes  are  likely  to  be  neces- 
sary until  the  presbyopic  period  of  life  arrives. 

SHOULD   THE   GLASSES    BE   WORX    COXSTAXTLY? 

This  is  a  question  that  frequently  arises,  and  it  is  one 
which  the  optician  will  be  called  upon  to  answer,  which  can 
only  be  done  by  taking  into  account  all  the  peculiarities  of 
each  individual  case,  with  special  reference  to  these  three 
points:  the  age  of  the  patient,  the  degree  of  the  hyperme- 
tropia, and  the  symptoms  of  which  he  complains. 

If  the  degree  of  the  defect  is  not  high,  and  the  patient  is 
young  and  ijti  vigorous  health,  and  the  eyes  are  strong  with 
distant  vision  perfect,  there  would  scarcely  seem  to  be  any  real 
necessity  for  their  constant  use.  When  such  a  person  is  en- 
gaged in  long-continued  sight-seeing,  as  at  a  theatre  or  at  an 
exposition,  symptoms  of  fatigue  of  the  eyes  may  appear,  when 
recourse  should  be  had  to  the  glasses.  Even  when  glasses  are 
not  worn  for  customary  distant  wear,  there  is  every  reason 
why  they  should  be  brought  into  use  on  such  special  occasions, 
in  order  to  assist  the  ciliary  muscle  and  lessen  the  strain  on 
the  eve. 


"•32  HVPERMETROPIA. 

WIIV   GLASSES   SHOULD    BE   WORN. 

In  many  cases  where  the  optician  may  find  it  necessary 
to  advise  his  patient  to  wear  the  glasses  constantly,  the  latter 
will  sometimes  protest  and  say  that  he  can  see  perfectly  well  at 
a  distance  without  them,  and  that  therefore  he  does  not  need 
them.  Under  such  circumstances  the  optician  must  take  the 
trouble  to  explain  the  reason  why  the  glasses  are  to  be  worn 
for  distance,  and  that  they  are  intended  not  so  much  to  im- 
prove vision  as  to  enable  the  patient  to  see  with  less  strain 
and  to  assist  the  ciliary  muscle,  which  is  overtaxed. 

If  the  patient  is  no  longer  young,  if  the  degree  of  hyper- 
metropia  is  marked,  or  if  there  is  much  pain  in  the  eyes,  and 
headache  and  symptoms  of  asthenopia,  then  in  any  or  all  of 
these  cases  the  use  of  glasses  for  constant  wear  is  no  longer  a 
question  or  a  matter  of  fancy,  but  becomes  an  actual  necessity. 
In  any  case  where  the  distant  vision  is  impaired  and  where  it 
is  raised  to  the  normal  standard  by  the  glasses,  there  is  suf- 
ficient reason  why  the  glasses  should  be  used  for  constant 
wear. 

The  fact  is  that  when  hypermetropia  exists  in  any  marked 
degree,  no  amount  of  resting  the  eyes  nor  the  observance  of 
any  fixed  rules  can  possibly  prevent  such  eyes  from  becoming 
weak  and  painful  in  the  absence  of  convex  glasses,  which  will, 
when  regularly  made  use  of,  do  much  to  render  them  more 
useful  and  comfortable. 

In  the  prescribing  of  glasses  two  objects  must  be  kept  in 
view :  to  select  that  glass  which  will  afford  the  greatest  acute- 
ness  of  vision,  Avhich  results  only  when  the  rays  of  light  are 
sharply  focused  on  the  retina,  thus  producing  a  distinct  image. 
This  sharp  focus  may  be  effected  by  the  accommodation  alone, 
by  a  convex  lens  alone  (as  in  an  eye  under  atropine),  or  by  a 
•combination  of  action  of  a  convex  lens  and  the  accommodation ; 
and  hence  the  optician  must  make  the  effort  to  so  associate 
the  glasses  and  the  accommodation  that  this  clearly  defined 
focus  may  be  maintained.  In  the  second  place,  that  glass 
should  be  chosen  which  will  enable  the  eyes  to  perform  their 
Junctions  with  the  greatest  ease  and  comfort. 


IIYPER.METROPIA.  63 


A  COMMON  COMPLAINT. 


It  frequently  happens  that  when  convex  glasses  are  first 
^iven  to  a  hypermetropic  person  for  constant  wear,  they  will 
make  objects  appear  magnified,  and,  therefore,  closer  than 
they  really  arc.  Such  a  person  may  return  to  the  optician  with 
the  complaint  that  the  pavement  seems  to  approach  him,  and 
therefore  he  feels  as  if  he  was  walking  up-hill  or  taking  a  step 
upward.  It  may  be  well  for  the  optician  to  make  a  reexam- 
ination, so  as  to  be  sure  that  the  glasses  that  have  been  pre- 
scribed are  not  at  fault,  and  then  the  patient  should  be  assured 
that  if  he  will  persist  in  their  use  these  annoying  appearances 
will  speedily  pass  away  and  the  sight  will  become  so  natural 
that  he  will  scarcely  be  conscious  of  having  glasses  before  his 
eyes. 

Kl  J.KS    FOR   DF.TKRMIXIXG    i  1 1 F   GLASSES. 

Some  authorities,  instead  of  prescribing  the  strongest 
convex  lenses  with  which  the  patient  retains  his  full  acuteness 
of  vision,  think  it  best  to  order  a  lens  somewhat  weaker,  per- 
haps .50  D.  to  .75  D.  less,  and  in  this  way  they  feel  confident 
the  eyes  will  at  oi: ?e  take  kindly  to  the  glasses,  and  will  begin 
to  reap  the  benefit  to  be  derived  from  their  use  at  the  start, 
whereas  the  stronger  ones  would  probably  annoy  the  eyes  at 
first  and  might  require  some  time  before  they  became  habitu- 
ated to  them. 

In  cases  where  atropine  has  been  applied,  Donders  ad- 
vised the  prescribing  of  a  glass  that  would  correct  all  the  man- 
ifest hypermetropia  and  one-fourth  of  the  latent.  Another 
author  recommends  a  convex  lens  equal  in  strength  to  one- 
half  the  sum  of  the  manifest  and  the  total  error.  For  example. 
if  the  manifest  error  was  2  D.  and  the  total  error  4  D..  the 
sum  of  the  two  would  equal  6  D.,  and  the  glasses  ordered 
would  be  -f  3  D.  This  last  rule  can  scarcely  be  considered  a 
scientific  one.  and,  in  fact,  neither  of  these  rules  appeals  to 
the  optician,  as  they  are  both  based  on  measurements  made 
under  atropine.  We  repeat,  then,  and  would  emphasize  the 
advice,  that  the  optician  should  not  attempt  to  do  more  than 
correct  the  manifest  error. 


64  iiyrERMETRoriA. 


DONDERS    WORDS. 


■"He  wlu)  knows  by  experience  how  coninionly  hyi)cr- 
metropia  occurs,  how  necessary  a  knowledge  of  it  is  to  the 
correct  diagnosis  of  the  various  defects  of  the  eye,  and  how 
deeply  it  affects  the  whole  treatment  of  the  oculist,  will  come 
to  the  sad  conviction  that  an  incredible  number  of  patients 
have  been  tormented  with  all  sorts  of  remedies,  and  have 
been  given  over  to  painful  anxiety,  who  would  have  found 
immediate  relief  and  deliverance  in  suitable  spectacles." 

These  words  are  as  true  now  as  wdien  first  uttered  by  our 
distinguished  teacher,  and  they  have  been  verified  by  the  ex- 
perience of  many  persons  who  have  had  this  defect  from 
childhood  and  who  have  suffered  greatly  while  attending 
school,  but  who  did  not  understand  the  cause  of  their  distress 
until  they  grew  up  and  learned  the  nature  of  hypermetropia. 

BEFORE    HYPERMETROPIA    WAS    UNDERSTOOD. 

Such  persons  were  unable  to  use  their  eyes  for  any  lengllr 
of  time,  and  therefore  failed  to  complete  their  studies,  and  in 
this  way  fell  behind  their  classmates  and  appeared  to  be  stupid. 
If  they  complained  of  pain  in  the  eyes  or  headache,  it  was 
regarded  as  an  excuse  to  get  aw-ay  from  their  books.  Occa- 
sionally such  a  child  would  chance  upon  a  pair  ol  grandfather's 
<liscarded  spectacles,  and,  wdth  childlike  curiosity,  would  tr>' 
them  on,  when  it  found  to  its  amazement  that  it  could  read 
with  comfort,  and  the  print  seemed  large  and  plain.  Ol" 
course,  as  soon  as  it  was  discovered  in  this  presumptuous  use 
of  the  old  spectacles,  the  latter  were  taken  away  and  the  child 
warned  never  to  touch  them  again  under  penalty  of  losing 
its  sight  and  becoming  blind.  While  the  parents  acted  entirely 
for  the  best  interests  of  the  child  according  to  their  own  limited 
knowledge,  yet  to  us  of  this  day,  w-ho  are  so  familiar  with  the 
symptoms  of  hypermetropia  and  its  method  of  correction  by 
convex  glasses,  this  deprivation  of  the  child  of  the  only  means 
of  relief  seems  little  short  of  barbarous. 

In  former  years  many  ambitious  young  men,  with  a  fond- 
ness for  study  and  high  hopes  for  professional  distinction, 
have  had  their  anticipations  nipped  in  tlic  1)U(1  l:)y  increasing 


HVPKRMETROl'IA.  ()5 

difficulties  cxpcricnccil  in  conliiuiccl  near  vision,  and  have  been 
advised  not  to  wear  glasses,  but  to  abandon  all  their  chosen 
plans  and  go  to  the  country  and  seek  some  occupation  that 
does  not  call  for  any  close  use  of  the  eyes.  Could  any  dis- 
appointment be  greater? 

There  are  many  pupils  attending  scIkjoI  at  the  present 
time  who  cannot  use  their  eyes  in  study  without  pain  and 
headache  and  irritation  of  the  eyes,  especially  noticeable  when 
they  are  used  by  artificial  light,  due  to  a  hypermetropia,  the 
correction  of  which  by  properly  adjusted  convex  glasses  would 
cause  these  annoying  symptoms  to  vanish  as  rapidly  as  the 
morning  dew  before  the  rising  sun.  Tlie  frequency  with 
which  these  cases  are  met  with  by  parents  and  educators  em- 
phasizes the  importance  of  an  early  recognition  of  the  cause, 
in  order  that  it  may  be  removed  before  permanent  injury  is 
done  to  the  sight,  and  that  the  complaints  of  children  and  their 
apparent  stupidity  may  receive  due  allowance,  and  not  be  met 
with  undeserved  punishment. 

I'ormerly  there  existed  a  great  prejudice  against  the  wear- 
ing of  convex  glasses  by  children,  which  doomed  them  to  a 
continuance  of  suffering  and  handicapped  them  in  the  acquire- 
ment of  an  education.  The  prevailing  idea  was  that  convex 
lenses  were  suitable  only  for  aged  persons  and  that  children 
were  debarred  from  their  use. 

A  TVnCAL  CASE  OF  HVPERMETKOPIA. 

In  order  to  point  the  moral  for  the  preceding  remarks, 
we  will  relate  the  history  of  a  typical  case,  which  was  originally 
reported  by  Dr.  Fenner. 

A  young  man  of  sixteen  years  comes  for  advice,  with  the 
statement  that  his  eyes  are  weak;  they  are  small,  prominent, 
and  set  widely  apart,  and  present  no  external  appearance  of 
disease.  The  pupils  act  quickly  and  freely  to  the  stimulus  of 
light.  On  inquiring  into  the  family  history  it  is  learned  that 
he  has  a  brother  who  suffers  like  himself,  but  to  a  less  degree, 
a  sister  who  has  convergent  strabismus,  and  his  father  was 
compelled  to  wear  glasses  at  the  age  of  thirty. 

The  patient's  health  is  good;  he  attends  school  and  is  in- 
clined to  be  studious,  but,  after  reading  or  writing  for  a  short 


66  HVIM-RMETROI'IA. 

time,  his  eyes  grow  tired  and  the  letters  become  indistinct. 
He  moves  the  book  further  from  his  eyes,  which  enables  him 
to  see  better  for  a  little  while,  but  soon  the  letters  begin  to 
blur  again ;  another  change  in  the  position  of  the  book  affords 
a  temporary  improvement,  which,  however,  is  soon  lost,  and 
any  further  changes  are  futile.  The  eyes  become  more  and 
more  fatigued,  there  is  a  slight  watering-  accompanied  by  a 
sensation  of  smarting  and  supra-orbital  pain,  the  print  pales 
and  the  borders  and  angles  of  the  letters  widen  out  so  that 
they  appear  as  confused,  irregular  spots  on  the  paper,  and  he 
is  compelled  to  discontinue  his  reading.  He  closes  his  eyes, 
rubs  and  presses  the  lids  with  his  fingers  for  a  few  moments, 
when  he  is  able  to  look  around  and  see  distant  objects  dis- 
tinctly. After  a  few  minutes  of  rest  in  this  way  he  is  again 
able  to  take  up  the  book  and  see  the  letters  with  their  original 
clearness,  but  the  eyes  give  out  sooner  than  before,  and  he 
goes  through  the  same  process  of  closing  his  eyes  and  com- 
pressing the  lids.  The  pain  over  his  eyes  increases  and  de- 
velops into  a  severe  headache,  the  conjunctiva  becomes  blood- 
shot, and  if  he  persists  in  reading  he  becomes  nauseated. 

Thus  he  worries  along  through  the  day,  and  if  he  attempts 
to  study  at  night  all  the  symptoms  are  intensified,  because  his 
eyes  are  sensitive  to  strong  artificial  light,  which  produces  a 
painful  dazzling  and  causes  a  sensation  of  scratching  and 
roughness  as  if  sand  was  under  the  lids.  When  he  awakes  in 
the  morning  he  finds  his  eye-lids  somewhat  adherent,  but 
after  washing  his  face  and  bathing  his  eyes,  he  feels  all  right 
again,  and  starts  in  with  his  studies  with  all  the  vim  and 
enthusiasm  of  an  ambitious  youth;  soon  the  well-known 
symptoms  return  and  he  goes  through  the  experience  of 
the  previous  day.  A  Sunday's  rest  invigorates  his  eyes, 
and  on  Monday  he  has  less  trouble  than  on  any  other  day, 
and  during  a  vacation  he  experiences  no  difficulty  whatever. 
He  says  he  has  been  under  the  treatment  of  a  physician,  who 
told  him  he  had  an  "afifection  of  the  optic  nerve,"  gave  him 
medicines,  blistered  his  temples,  and  dropped  "eye-water"  into 
his  eyes. 

On  examination  his  vision  is  found  to  equal  1^.  Con- 
vex lenses  were  tried,  conmiencing  with  -f  .50  D.,  and  increas- 


HVPKRMETROI'IA.  07 

ing  to  +  1.75  D.,  which  were  the  strongest  accepted;  -r  2  D. 
blurred  the  letters.  Hence,  his  manifest  hypermetropia  is 
+  1.75  D.  His  reading  vision  is  now  tried  and  his  amplitude 
of  accommodation  measured.  He  is  able  to  bring  the  print 
as  close  as  six  inches,  but  says  it  requires  an  appreciable 
effort;  he  gradually  moves  the  book  farther  away  as  he  reads, 
and  by  the  time  he  has  finished  the  paragraph  it  is  out  as  far 
as  fourteen  inches.  His  near  point  of  six  inches  represents 
an  amplitude  of  accommodation  of  6.50  D.,  and,  as  the  normal 
amplitude  at  this  age  is  ii  D.,  there  is  presumptive  evidence 
of  the  existence  of  4.50  D.  of  hypermetropia,  and,  as  the  mani- 
fest error  was  1.75  D.,  the  balance  exists  as  latent  hyper- 
metropia. 

Glasses  of  +  2  D.  are  ordered  for  him,  and  he  remarks, 
"Why,  doctor,  you  don't  want  me  to  wear  spectacles,  do  you?" 
"Certainly,"  the  oculist  answ^ers,  "or  at  least  I  wish  you  to  try 
them."  He  then  said,  "I  used  to  wear  my  grandmother's 
spectacles  at  night  to  get  my  lessons  and  I  could  see  as  well 
as  ever,  but  when  I  told  our  doctor  he  said  I  must  not  use 
any  more,  for  they  would  ruin  my  eyes  and  make  me  blind." 
Notwithstanding  his  doctor's  advice  he  takes  the  glasses,  re- 
turns to  school,  and  has  no  further  trouble  with  his  eyes. 

While  ignorance  of  these  matters  might  be  excused  in  the 
laity,  it  is  reprehensible  in  a  physician;  but  now,  since  the 
nature  of  the  defect  and  the  proper  means  of  correcting  it  are 
well  understood,  it  is  hoped,  by  the  diffusion  of  knowledge, 
to  overcome  the  prejudice  which  has  so  widely  existed  in  the 
public  mind  against  the  wearing  of  convex  glasses  by  children. 

TWO    IWIRS    OF   GLASSES. 

In  the  higher  degrees  of  hypermetropia.  and  in  hyperme- 
tropia of  persons  approaching  the  presbyopic  period  of  life, 
two  pairs  of  glasses  are  required — one  pair  for  distant  vision, 
and  the  other  pair  to  enable  fine  print  to  be  easily  read  at  the 
customary  distance. 

PROPER   FITTING   OF  GLASSES. 

It  should  l)c  remembered  that  when  strong  convex  glasses 
are  worn,  the  removal  of  the  lenses  a  little  farther  from  the 


68  HVl'KKMKTROI'IA. 

eyes  increases  their  i)o\ver  and  makes  them  ecjuivalent  to 
glasses  of  a  liioher  number;  and,  as  this  is  sometimes  not 
desirable,  it  would  not  be  out  of  place  for  the  optician  to  in- 
struct his  patient  just  how  they  should  be  worn. 

Another  point  that  should  not  be  overlooked  in  the  fitting 
of  such  glasses  is  to  see  that  they  are  close  enough  together 
that  the  patient  looks  through  the  centers  of  the  lenses  when 
converging  his  eyes  for  near  work,  as  otherwise,  if  the  line  of 
vision  was  through  the  edges  of  the  lenses,  the  rays  of  light 
would  be  refracted  as  by  prisms  with  curved  surfaces;  and, 
while  this  might  not  be  undesirable  in  selected  cases,  unless 
it  is  specially  indicated,  and  particularly  if  the  decentering  is 
outward,  it  might  destroy  the  harmony  betw'een  the  functions 
of  accommodation  and  convergence  and  be  productive  of 
asthenopic  symptoms. 

THE    PROPER   GLASSES. 

It  has  been  stated  on  a  previous  page  that  the  hyperme- 
tropic eye  is  unable  to  see  any  object  distinctly,  not  even  the 
most  remote,  without  an  elTort  of  accommodation,  and  the 
closer  the  object  the  more  the  strain.  Consequently,  in  hyper- 
metropic eyes  the  accommodation  is  in  a  state  of  constant 
tension. 

When  convex  glasses  are  placed  before  the  hypermetropic 
eye  it  is  found  that  the  ciliary  muscle,  which  has  been  in  a 
state  of  contraction  for  so  long  a  time,  cannot  wholly  relax; 
there  still  remains  a  certain  amount  of  involuntary  contrac- 
tion of  the  muscle,  but  this  is  an  element  that  cannot  be  meas- 
ured (except  by  atropine,  which  is  out  of  the  question),  and 
varies  in  different  individuals. 

Hence,  in  fitting  such  eyes  with  convex  lenses,  the 
strongest  they  will  bear  without  blurring  distant  vision  is  just 
equal  to  the  amount  of  relaxation  of  the  muscle  of  accommo- 
dation, and  this  is  known  as  the  manifest  hypermetropia.  The 
degree  of  involuntary  contraction  of  the  muscle  that  remains, 
is  the  measure  of  the  latent  hypermetropia,  with  vvhich  the 
optician  need  not  concern  himself,  as  he  will  have  done  his 
whole  duty  in  correcting  the  manifest  error. 

Sometimes  there  is  no  manifest  hypermetropia,  it  is  all 


HVPERMETROPIA.  G'.> 

latent,  which  is  particularly  the  case  in  younp:  persons.  At 
about  twenty  years  of  age  some  of  it  becomes  manifest,  the 
proportion  of  which  increases  with  advancing  years,  the  latent 
decreasing  in  the  same  ratio,  until,  finally,  in  middle  life  it  has 
entirely  disappeared,  and  all  of  the  hypermctropia  is  then 
manifest. 

A  CASE  OF  MANIFEST  II YPERMETROPIA  IN  WHICH  THE   LATENT 

PORTION  IS  REVEALED  BY  THE  DIMISHED  AMPLITUDE 

OF    ACCOMMODATION. 

Joseph  F.    Aged  twenty-one  years. 

Has  no  trouble  in  using  his  eyes  in  daytime,  but  com- 
plains of  inability  to  read  at  night.  He  went  to  an  optician, 
who  gave  him  a  pair  of  +  .50  D.  glasses,  but  they  have  not 
been  of  much  benefit  to  him.  On  examination  his  vision  is 
found  to  equal  \^  and  a  manifest  hypermctropia  of  .50  D.  A 
test  of  his  reading  vision  showed  a  range  of  accommodation 
of  eight  inches  to  thirty-three  inches. 

A  near  point  of  eight  inches  indicates  an  amplitude  of 
accommodation  of  only  5  D.,  whereas  the  normal  amplitude 
of  a  person  at  this  age  is  at  least  9.50  D.,  and  hence  we  are 
justified  in  assuming  the  existence  of  4.50  D.  of  total  hyper- 
mctropia;  and  as  the  test  showed  only  .50  I),  of  manifest  error, 
there  remains  4  D.  of  latent  defect.  It  was  not  deemed  advis- 
able to  correct  the  total  error,  and  hence  his  reading  vision 
was  tested  with  the  following  results: 

With       1  D.,  range  of  accommodation  7     in.  to  33  in. 

1501)., .5J4     "     :?;?  " 

•J  II.,      .")        "     32  " 

+  2  D.  glasses  were  ordered  for  reading,  and  gave  the  most 

perfect  satisfaction. 

A    CASE    OF    SLIGHT    MANIFEST   AND    MARKED    LATENT 
HVPERMETROPIA. 

Mrs.  S.  M.  R.    Aged  thirty-eight  years. 

Eyes  have  been  failing  for  the  past  year.  Has  constant 
headache  and  a  great  deal  of  pain  and  smarting  in  eyes.  Com- 
plains that  she  can't  see  to  thread  a  needle.  \'ision  ~  y|. 
Manifest  Hy.  =  .50  D.  The  near  point  has  receded  to  sixteen 
inches,    which    implies    an    amplitude    of    accommodation    of 


70  HYI'EKMHTROPIA. 

J. 50  1).,  ami.  as  the  normal  amplitude  at  this  age  is  about  5  D., 
we  liave  evidence  of  2.50  D.  of  hypernietropia. 

It  is  a  curious  coincidence  that  if  we  calculate  the  reading- 
glasses  according-  to  the  rules  given  under  Presbyopia  the 
same  result  is  obtained.  Subtract  the  glass  representing  the 
receded  near  point  (16  in.  —  2.50  D.)  from  the  glass  repre- 
senting the  point  which  we  wish  to  make  the  near  point  (8 
in.  =  5  D.),  which  leaves  +  2.50  D.  as  the  glass  required. 

One  would  expect  at  this  age  that  more  of  the  latent  por- 
tion would  become  manifest,  and  that  it  has  not  indicates  an 
exceptionally  vigorous  condition  of  the  accommodation. 
Glasses  of  +  2.50  D.  were  ordered  for  reading,  and  for  dis- 
tance +  .75  D.  will  answer  at  present,  although  stronger  ones 
will  soon  be  needed,  as  the  latent  trouble  becomes  manifest. 

A     CASE     OF     IIVPER.METROPIA     IN     WHICH     READING     GLASSES 

FAILED     TO      GIVE     SATISFACTION      UNTIL     DISTANCE 

GLASSES   WERE   WORN. 

Mrs.  J.  H.  S.    Aged  fifty-nine  years. 

Her  eyes  have  been  troubling  her  for  past  fifteen  years, 
and  she  has  great  difficulty  in  getting  glasses  to  suit.  Has 
been  compelled  to  change  glasses  frequently,  those  for  reading 
at  present  being  +  4  D.,  with  which  she  can  see  fairly  well, 
but  in  spite  of  this  they  do  not  give  her  satisfaction.  Vision 
=  I5.  With  -r  1.50  D.  -  j|.  Ordered  +  1.50  D.  for  dis- 
tance and  constant  wear,  and  advised  her  to  continue  the  -|-  4 
D.  glasses  for  reading. 

In  this  case  the  uncorrected  hypermetropia  kept  the  eyes 
on  a  constant  strain,  and  consequently  when  the  patient  de- 
sired to  read  she  commenced  the  task  wdth  eyes  already 
fatigued,  and,  therefore,  her  reading  glasses  did  not  seem  suit- 
able, even  though  they  were  accurately  adjusted  for  their  pur- 
pose. But,  now  that  her  reading  glasses  are  supplemented  by 
distance  ones,  the  constant  strain  will  be  relieved,  and  when 
she  begins  to  read  her  eyes  will  be  fresh  and  the  reading 
.glasses  prove  all  that  can  be  desired. 

There  has  been  a  marked  change  of  late  years  in  the  atti- 
tude of  the  public  in  regard  to  the  wearing  of  convex  glasses, 
and  when  their  use  is  imperatively  demanded  for  the  rectifica- 


HYl'HRMKTROPIA.  71 

tion  of  some  optical  defect,  there  is  at  least  no  stubborn 
protest ;  but  there  is  still  room  for  improvement,  and  instead  of 
this  placid  acquiescence  in  their  employment  we  would  like 
to  see  such  a  sentiment  prevail  as  would  recognize  their  worth 
and  demand  their  use  wherever  and  whenever  indicatcfl. 

cAKi'.  IN  Till':  u  i.AKixc  OF  ( ;i,Assi:s. 

When  glasses  are  i)rcscribed  ft^r  the  correction  of  hyper- 
metropia.  whether  for  constant  wear  or  only  for  readinj^,  the 
optician  should  give  his  patient  definite  instructions  that  he 
wear  them  always  for  the  purpose  for  which  they  are  given. 
If  they  are  laid  aside  at  intervals,  a  return  of  the  old  symptoms 
is  apt  to  follow,  and  in  this  way  little  progress  can  be  made  in 
relieving  the  eyes  and  freeing  them  from  irritation.  Whereas, 
if  the  glasses  are  worn  persistently,  comfort  is  at  once  experi- 
enced and  the  eyes  become  better  and  stronger,  so  much  so,  in 
some  cases,  that  the  glasses  may  be  dispensed  with  for  general 
wear  and  used  only  for  reading. 

In  young  persons,  whose  eyes  are  strong  enough  to  easily 
overcome  the  hypermetropia,  whose  distant  vision  is  good,  and 
who  experience  no  trouble  except  in  reading,  the  glasses  may 
be  given  with  the  distinct  understanding  that  they  need  be 
worn  only  for  close  use.  As  the  patient  grows  toward  the 
presbyopic  period  of  life,  these  glasses  will  need  to  be  ex- 
changed for  those  of  a  higher  power,  and  then  the  old  pair 
will  sufificc  for  distant  vision  and  should  be  used  for  that 
purpose. 

In  the  case  of  intelligent  persons  who  are  desirous  to  be 
properly  fitted  the  use  of  the  trial  case  is  the  decisive  method, 
and  the  test  that  is  suflficiently  trustworthy  is  the  patient's  own 
statement  that  such  or  such  a  lens  does  not  blur  the  sight,  or 
makes  vision  clearest,  or  feels  the  most  comfortable  to  his  eyes. 

But  in  the  case  of  stupid  persons,  or  of  children,  where 
definite  answers  can  only  be  obtained  with  the  greatest  diffi- 
culty, or  where  it  is  desired  to  verify  the  statements  made,  the 
optician  should  have  recourse  to  his  ophthalmoscope  and 
retinoscope.  the  latter  especially  affording  an  inexpensive  and 
satisfactory  methcnl  of  determining  the  state  of  the  refraction. 
Even  with  the  assistance  afforded  bv  these  additional  methods, 


72  IIVPKR.MRTROl'IA. 

some  cases  will  still  he  obscure,  and  the  optician  nuist  fall  hack 
on  his  own  exiK^rience  and  he  g^uided  by  general  principles, 
ahvays  endeavoring-  to  press  the  patient  to  the  most  satisfac- 
tory answers  oljtainahle. 

There  is  no  limit  of  age  as  regards  the  wearing  of  convex 
glasses  for  hypermetropia  (or  in  using  the  ]>roper  glasses  for 
the  correction  of  any  other  ojnical  defect).  They  may  be 
placed  before  the  eyes  of  a  child  as  soon  as  he  is  old  enough 
to  understand  that  they  are  not  playthings,  that  being  about 
the  age  when  the  child  commences  to  go  to  schooJ.  In  those 
cases  of  hypermetropia  which  tend  to  produce  squint,  the  per- 
sistent wearing  of  convex  glasses  will  usually  prevent  this 
tendency  from  being  developed.  For  the  same  reasons,  they 
should  be  worn  after  an  operation  for  strabismus,  as  a  pre- 
ventive of  a  return  of  the  defect. 

THE    PrXCTl'M    KE.MOTL'M    IX    II  Vl'ERM  KTROl'I.V. 

The  emmetropic  eye,  when  at  rest,  has  been  shown  to  be 
adapted  for  parallel  rays,  or  those  ]iroceeding  from  infinite 
distance,  consequently  its  punctum  remotum  is  said  to  lie  at 
infinity.  The  hypermetropic  eye,  on  the  other  hand,  is 
adapted  only  for  convergent  rays;  but  there  are  no  convergent 
rays  in  nature,  and  consequently  such  an  eye  is  adjusted  for 
a  condition  that  does  not  exist.  The  focus  of  parallel  rays 
lies  behind  the  retina,  and  the  punctum  remotum  becomes  a 
negative  quantity  in  hypermetropia. 

The  position  of  this  negative  point  can  be  found  by  (or,  in 
other  words,  the  distance  of  the  punctum  remotum  behind  the 
eye  will  be  equal  to)  the  focus  of  the  convex  lens  wdiich  is 
required  to  correct  the  hypermetropia.  The  writer  finds  that 
this  subject  is  not  clearly  comprehended  by  the  optical  student, 
and  a  glance  at  the  various  standard  text-books  shows  such 
conflicting  and  ambiguous  statements  that  there  is  no  wonder 
the  reader  is  puzzled  and  confused  and  unable  to  gather  a 
proper  understancHng  of  it.  And  as  it  is  a  matter  of  consider- 
able theoretical  importance,  we  will  endeavor  to  describe  it  so 
clearly  that  the  beginner  of  the  study  cannot  fail  to  understand. 


HYPERMETROPIA. 


This  illustration  shows  the  punctuni  reniotuni  oi  the 
hypermetropic  eye  and  the  lenses  that  give  to  parallel  rays 
sufficient  converg-ence  to  meet  upon  its  retina. 

The  location  of  the  far  point  behind  the  eye  is  the  spot  to 
which  rays  must  converge  before  entering  the  eye,  in  order 
that  they  may  be  focused  upon  the  retina.  From  this  state- 
ment v^e  are  enabled  to  formulate  the  following  corollary: 
The  hypermetropic  eye,  when  its  accommodation  is  at  rest  and 
its  refractive  power  at  a  minimum,  is  adjusted  for  rays  con- 
verging to  its  far  point,  and  such  converging  rays  exactly 
meet  upon  its  retina. 


The  focus  of  a  convex  lens  is  at  a  certain  definite  distance 
<lepending  upon  the  refractive  power  of  the  lens,  and  therefore 
the  convex  lens  that  is  needed  to  give  to  the  rays  the  proper 
convergence,  so  that  if  continued  they  wotdd  meet  at  the 
punctum  proximum,  which  holds  a  conjugate  relation  to  the 
retina,  must  be  a  lens  whose  focal  distance  exactly  corresponds 
to  this  point. 

In  the  diagram  of  the  hypermetropic  eye,  given  above, 
the  position  of  the  focus  of  parallel  rays  is  at  F,  which  is  a 
certain  distance  behind  the  retina,  and  the  convex  lens  imme- 
diately below  its  brings  parallel  rays  also  to  a  focus  at  F,  which 
is  a  corresponding  point.  If  now  this  convex  lens  be  raised 
to  a  position  just  in  front  of  the  diagramatic  eye.  and  almost 
touching  the   cornea,    it   is   evident   that   tlic    rays   that    pass 


t-i  IIYI'KRMKTROPIA. 

throii^li  it  ami  enter  tlie  eye  will  possess  just  the  proper  C(jn- 
vergence  to  be  focused  on  the  retina  of  the  eye,  and  hence  this 
lens  will  be  the  proper  one  to  correct  the  hypermetropia. 

If  the  lens  was  placed  farther  from  the  eye  a  weaker  one 
would  suffice,  because,  the  puncttmi  rcmottmi  remaining-  at 
the  same  point,  the  farther  the  kns  is  removed  from  it  the 
less  refractive  power  it  needs  to  focus  parallel  rays  at  this 
point.  This  fact  is  well  illustrated  in  the  diagram,  where  the 
second  lens  is  removed  from  the  eye,  and  although  of  weaker 
power  has  its  focus  at  the  corresponding  point  F.  Tlierefore, 
when  the  convex  correcting  lens  is  to  be  worn  a  definite  dis- 
tance in  front  of  the  eye,  it  must  be  of  a  certain  strength;  if 
it  is  approached  closer  to  the  eye  its  strength  must  be  in- 
creased; if  it  is  removed  farther  from  the  eye  a  weaker  lens 
will  answer. 

FAULT V    CONCEPTIONS    OF    HYPERMETROPIA. 

So  much  has  been  written  of  late  years  as  to-  the  growing 
prevalence  of  myopia  and  its  direct  causation  by  the  increased 
use  of  the  eyes  for  reading  and  writing  that  is  required  by 
our  habits  of  civilization,  that  we  are  almost  imconsciously 
led  to  regard  it  as  the  most  common  error  of  refraction.  This 
impression  is  heightened  by  the  fact  that  myopia  can  with 
difficulty  be  concealed,  and  we  readily  recognize  it  by  the 
stooping  position,  by  the  nearness  with  which  the  book  is  held, 
and  by  the  well-known  nipping  of  the  eyelids  together.  But 
the  fact  is  that  hypermetropia  is  the  most  frequent  defect, 
although  it  is  not  patent  to  others,  and  even  the  individual 
himself  for  a  long  time  may  not  be  aware  of  it  until  an  im- 
paired condition  of  health,  or  a  severe  attack  of  illness,  or  the 
approach  of  the  presbyopic  period  of  life  makes  it  manifest 
by  an  unmistakable  train  of  symptoms. 

When  these  evidences  of  the  defect  become  noticeable,  as 
they  are  especially  apt  to  do  after  a  prolonged  use  of  the  eyes, 
it  seems  natural  to  place  them  in  the  relation  of  cause  and 
efifect ;  the  one  follows  the  other,  and  would  seem  to  be  directly 
produced  by  it.  While  this  may  be  said  of  myopia,  it  is  not 
true  of  hypermetropia;  no  amount  of  abuse  or  overtaxing  the 
eyes  can  result  in  the  production  of  hypermetropia,  or  can  in- 


HYPERMETROPIA.  /.) 

crease  it  when  already  present.  Of  course,  any  immoderate 
use  of  the  eyes  will  agg"ravate  the  symptoms  and  render  the 
eye  apparently  weaker,  but  it  cannot  originate  the  essential 
condition  of  hypermetropia,  an  undeveloped  or  flat  eye-ball, 
which  is  a  congenital  condition. 

.\nother  error  that  has  crept  in  and  gained  credence,  is 
the  supposition  that  hypermetropia  is  better  for  distant  vision 
than  emmetropia.  The  fact  that  its  far  point  is  negative  and 
that  the  hypermetropic  eye  is  adapted  for  a  point  beyond 
infinity,  shows  that  its  accommodation  is  under  a  constant 
strain,  and  therefore  its  distant  vision  suffers  from  the  disad- 
vantage of  being  accomplished  only  at  this  expense.  Whereas 
the  emmetropic  eye  by  nature  is  adjusted  for  the  parallel  rays 
of  distant  vision,  and  no  other  form  of  eye  can  be  better  than 
this. 

Xo  well-read  optician  should  fall  into  the  error  of  sup- 
posing that  a  person  must  be  myopic  simply  because  he  holds 
his  book  close.  Attention  has  already  been  called  in  the 
earlier  part  of  this  chapter  to  the  fact  that  in  high  degrees  of 
hypermetropia  the  book  is  sometimes  approached  quite  near 
to  the  eyes,  and  the  caution  was  given  not  to  mistake  hyper- 
metropia for  myopia,  and  a  number  of  cases  illustrative  of  this 
point  were  narrated.  This  matter  is  of  such  great  importance 
as  to  call  for  a  repetition  at  this  place,  while  mentioning  some 
false  conceptions  about  hypermetropia. 

SEQUEL.^     OF     HYPERMETROPIA     OR     ITS     DELETERIOUS     CON- 
SEQUENCES. 

All  the  defects  of  the  optical  construction  of  the  eye,  and 
especially  those  that  impose  an  unnatural  tax  upon  the  ac- 
commodation, are  not  only  accompanied  by  a  certain  train  of 
symptoms,  but  are  liable  to  lead  to  the  production  of  other 
troubles.  Tlie  evil  effects  flowing  from  hypermetropia  may 
be  enumerated  as  follows: 

1.  Headache  and  neuralgia. 

2.  Spasm  of  accommodation. 

3.  Blepharitis,  styes,  etc. 

4.  Glaucoma. 


76  HYPERMETROFI.V. 

5.  Cataract. 

6.  Myopia. 

7.  Asthenopia. 

8.  Converg-ent  strabismus. 

9.  Retinitis  and  neuritis. 
10.  Nervous  derang-ements. 

I.       IIEAnACHE    AM)    XKIRALGIA. 

These  forms  of  paroxysmal  pain  are  very  common,  and 
there  is  scarcely  a  family  but  can  disclose  one  or  more  suf- 
ferers. There  is  usually  no  direct  evidence  of  actual  disease  of 
the  aflfected  nerves  or  brain,  or  even  of  any  of  the  vital  organs 
of  the  body,  and  yet  there  must  be  some  underlying  cause 
in  every  case  of  intractable  headache  or  neuralgia.  These 
ailments  may  be  classified  under  several  dififerent  headings, 
but  by  far  the  most  common  form,  and  the  one  in  which  the 
optician  is  particularly  interested,  is  the  reflex. 

Under  this  head  (of  reflex  troubles)  may  be  mentioned  the 
headaches  and  neuralgias  that  result  from  a  decayed  tooth, 
hardened  wax  in  the  ear,  disease  or  obstruction  of  the  nasal 
cavities,  some  obscure  rectal  or  pelvic  irritation,  and  lastly, 
and  most  important  from  our  standpoint,  those  that  are  caused 
by  some  error  of  refraction  or  some  anomaly  of  the  ocular 
muscles.  No  one  can  deny  that  remarkable  cures  of  head- 
ache and  neuralgia  have  been  accomplished  solely  by  the 
removal  of  one  of  the  causes  mentioned  above,  and  without 
the  use  of  drugs. 

Therefore,  in  any  case  of  intractable  headache  and  neu- 
ralgia, the  condition  of  the  refraction  of  the  eye  and  of  its 
muscular  equilibrium  should  be  carefully  inquired  into;  and 
when  the  family  physician  has  such  a  case  under  his  care  and 
does  not  himself  possess  the  skill  or  the  instruments  required 
to  make  the  necessary  examination,  he  should  refer  his  patient 
to  a  skilled  optician  in  whom  he  has  confidence,  in  order  that 
this  source  of  suffering  may  be  removed. 

Many  cases  of  headache  have  been  treated  by  the  physi- 
cian on  the  presumption  of  cerebral  congestion  or  cerebral 
anaemia,  by  the  remedies  that  are  ordinarily  useful  in  such  con- 
ditions, wthout  benefit;  and,  finally,  after  every  other  hope  of 


HYPERMETROPIA.  il 

relief  had  failed,  the  thought  has  occurred  that  perhaps  the 
eyes  were  at  fault,  and  recovery  immediately  followed  the 
proper  correction  of  any  existing  anomaly. 

The  literature  on  this  subject  of  headaches  and  neuralgia 
due  to  eye-strain  is  very  extensive,  and  within  the  last  few 
years  there  has  been  a  large  amount  of  additional  testimony 
to  prove  the  importance  of  a  thorough  examination  of  the 
eyes  in  all  cases  of  headache.  It  is  proper  to  state  that  cor- 
rection of  the  ocular  anomaly  does  not  always  cure  the  pain 
in  the  head  immediately;  sometimes  the  relief  comes  gradu- 
ally, and  again  a  course  of  constitutional  treatment  may  be 
necessary  in  addition. 

2.       SPASM  OF  ACCOMMODATION. 

The  constant  contraction  of  the  ciliar}-  muscle  in  hyper- 
metropia  that  is  necessary  to  overcome  the  refractive  error  and 
afford  clear  vision,  often  gives  rise  to  the  condition  known  as 
"spasm  of  the  accommodation,"  which  is  simply  a  high  tension 
and  persistent  contraction  of  the  affected  muscle.  Such  spasm 
is  apt  to  occur  in  persons  of  a  nervous  temperament,  and, 
strange  to  say,  it  bears  no  direct  relation  to  the  vigor  of  the 
accommodation;  that  is,  persons  with  a  strong  and  vigorous 
accommodation  may  never  be  troubled  in  this  way,  whereas 
patients  with  a  relatively  feeble  accommodation  may  suffer 
with  a  marked  cramp  of  the  ciliary  muscle. 

The  symptoms  of  spasm  of  the  accommodation  are  photo- 
phobia (dread  of  light),  lachrymation  (excessive  watering  of 
the  eyes),  pain,  contracted  pupils  and  congestion  of  the  eye. 
In  addition  to  these  symptoms,  distant  vision  is  impaired  and 
there  is  a  condition  of  false  or  simulated  myopia,  so  marked 
that  concave  glasses  have  been  ordered  on  account  of  the  im- 
provement they  afford  in  distant  vision;  this,  however,  is  a 
grievous  error  that  should  not  be  committed  by  any  well- 
informed  optician.  Tbe  cause  of  spasm  of  the  accommotlation 
is  not  limited  to  hypermetropia. 

3.       BLEPHARITIS,    STYES,    ETC. 

The  constant  strain  under  which  the  hypermetropic  eye 
labors  causes  an  increasetl  flow  of  lilood  to  the  organ,  which 


78  HYPERMETROPIA. 

results  in  a  congestion  of  some  of  the  structures  of  the  eye  and 
a  subsequent  intlamniation.  In  this  way  the  edges  of  the  Hds 
become  red  and  swollen,  with  the  formation  of  scales  and 
crusts,  and  the  dropping  out  of  the  lashes,  which  are  some- 
times not  reproduced.  Tlie  statement  has  been  made  by  com- 
petent authorities  that  "chronically  inflamed  eye-lids  are 
almost  always  dependent  upon  hypermetropia  or  hyperme- 
tropic astigmatism." 

This  congestion  may  result  in  a  localized  inflammation, 
and  there  are  few  diseases  of  the  lids  more  common  or  more 
annoying  than  styes,  oftentimes  one  following  another  in  quick 
succession,  seeming  to  come  without  any  apparent  cause. 
The  inflammation  is  seated  in  and  around  the  bulb  of  an  eye- 
lash, and  rapidly  results  in  the  formation  of  pus,  which  breaks 
naturally  or  is  discharged  by  a  small  incision  made  in  the  apex 
of  the  tumor.  The  cause  is  usually  to  be  found  in  some  ocular 
anomaly,  principally  hypermetropia,  and  the  treatment  consists 
in  the  correction  of  the  error  by  properly  adjusted  glasses. 

4.       GLAUCOMA. 

This  is  a  disease  characterized  by  abnormally  increased 
intra-ocular  tension,  which  gradually  advances  to  blindness. 
The  majority  of  the  cases  of  this  dreaded  disease  occurs  in 
hypermetropic  eyes,  and  hence  the  value  of  correcting  glasses 
becomes  evident  as  a  means  of  prevention.  In  one  of  the 
latest  text-books  on  diseases  of  the  eye,  the  statement  is  made 
that  "overuse  of  the  eyes,  especially  with  improperly  corrected 
refractive  error,  has  a  distinct  tendency,  by  causing  ocular  con- 
gestion, to  bring  on  glaucoma  in  an  eye  predisposed  to  the 
disorders  by  changes  in  the  ciliary  region." 

5.       CATARACT. 

Investigations  by  competent  authorities  show  that  the 
majority  of  cataractous  eyes  are  hypermetropic,  and  it  follows 
that  the  use  of  the  proper  correcting  glasses  must  be  looked 
upon  as  an  important  preventive  measure. 

6.       MYOPIA. 

Hypermetropia  is  the  prevalent  condition  of  refraction 
in  childhood,  and  the  strain  caused  by  this  defect  in  the  use 


HVPERMETROPIA.  t^) 

of  the  eyes  during  these  tender  years,  for  reading  and  studying 
for  long  periods  of  time  and  under  unfavorable  conditions,  re- 
sults in  an  elongation  of  the  eye-ball  and  the  development  of 
myopia.     This  has  been  proven  by  abundant  statistics. 

7.      ASTHENOPIA. 

This  term  means  weak  sight,  and  may  be  defined  as  a  lack 
of  suilficient  muscular  strength  to  maintain  for  any  length  of 
time  the  adjustment  of  the  dioptric  apparatus  required  for  near 
vision.  It  may  be  divided  into  muscular  and  accommodative, 
the  latter  being  the  form  which  occurs  as  the  result  of  hyper- 
metropia,  for  the  reason  that  a  portion  of  the  accommodation 
is  diverted  from  its  legitimate  purposes  of  focusing  the  eye  for 
near  vision  and  used  for  uniting  the  parallel  rays  from  distant 
sources,  thus  leaving  a  corresponding  deficiency  in  the  power 
of  adjustment  for  close  use,  and  requiring  an  unnatural  tension 
of  the  muscle  of  accommodation  for  the  latter  purpose.  The 
result  is  that  the  muscles  become  exhausted  and  symptoms  of 
asthenopia  make  their  appearance. 

Asthenopia  does  not  usually  manifest  itself  in  young  per- 
sons, because  their  accommodation  is  sufificiently  vigorous  to 
overcome  the  hypemietropia  without  feeling  the  strain,  and 
because  they  are  seldom  required  to  use  their  eyes  for  any 
considerable  length  of  time  in  looking  at  small  objects.  But 
after  the  age  of  ten  years,  when  the  accommodation  naturally 
begins  to  gradually  fail,  and  when  more  and  longer  use  of  the 
eyes  is  required  for  reading.  WTiting  and  studying,  then  the 
symptoms  of  asthenopia  begin  to  be  apparent,  cause  much 
annoyance  and  suffering,  and  even  give  rise  to  painful  fore- 
bodings of  future  blindness. 

In  asthenopia  there  may  be  comfortable  vision  for  a  sliort 
time,  but  the  necessary  effort  of  accommodation  required  for 
close  vision  cannot  be  long  maintained,  and,  notwithstanding 
an  increased  nervous  impulse  is  transmitted  to  the  eye  to  com- 
pensate for  the  unnatural  tension  that  is  called  for,  there  are 
soon  a  feeling  of  fatigue  within  the  eyes,  pain  in  and  around 
them,  excessive  irritability,  and  a  blood-shot  appearance  of  the 
conjunctiva.  \'ision  becomes  blurred,  and  the  constant  strain- 
ing of  the  accommodation  to  form  clear  images  aggravates 


80  HYPERMETROriA. 

all  the  symptoms,  renders  the  eye  sensitive  to  light,  particu- 
larly if  it  be  artificial,  causes  a  painful  dazzling  and  a  sensation 
of  smarting-  and  roughness  as  if  there  was  sand  beneath  the 
lids;  there  is  often  a  resulting  conjunctivitis  with  swelling  of 
the  lids  and  soinetimes  a  mucous  discharge,  which  dries  during 
sleep  and  causes  the  edges  of  the  lids  to  adhere. 

The  patient  is  inclined  to  close  his  lids  and  rub  his  eyes  or 
press  them  with  his  fingers,  and,  after  a  short  period  of  rest, 
all  the  symptoms  disappear;  but  they  return  with  increased 
violence  after  another  attempt  to  use  the  eyes  in  close  vision, 
until,  finally,  the  pain  and  irritation  become  so  great  that 
reading,  writing,  sewing  and  all  fine  work  have  to  be  aban- 
doned, and  some  occupation  sought  that  does  not  call  for  use 
of  the  eyes  in  sharp  vision  of  small  objects. 

The  treatment  of  asthenopia  is  the  removal  of  the  cause 
by  the  correction  of  the  hypermetropia. 

8.       CONVERGENT    STRABISMUS. 

In  this  form  of  strabismus  the  visual  line  of  one  eye  is 
dircted  to  the  object  looked  at,  while  the  visual  line  of  the 
other  eye  is  deviated  inward,  and  in  four-fifths  of  all  cases  it 
is  caused  by  (or  at  least  it  is  associated  with)  hypermetropia; 
and  therefore  it  is  fair  to  presume  that  this  condition  of  squint 
might  have  been  corrected  by  the  timely  use  of  glasses. 

When  convergent  strabismus  is  due  to  hypermetropia,  it 
usually  makes  its  appearance  about  five  or  six  years  of  age, 
at  the  time  when  pictures,  letters  of  the  alphabet,  and  small 
objects  are  first  noticed.  Sometimes  it  does  not  show  itself 
until  after  the  child  has  been  attending  school  for  a  time, 
when  the  close  use  of  the  eyes  is  more  pronounced  and  more 
persistent.  There  is  scarcely  any  ailment  that  may  befall  a 
child  that  will  cause  more  alarm  to  the  anxious  mother  than 
the  appearance  of  strabismus;  and  a  cross-eyed  child  in  a 
family  is  something  to  be  greatly  dreaded,  not  only  on  account 
of  the  impairment  of  vision  in  the  scjuinting  eye,  but  also  be- 
cause of  the  unpleasant  disfigurement. 

The  explanation  of  the  production  of  convergent  strabis- 
mus by  hypermetropia  is  as  follows:  The  presence  of  this  error 
of  refraction  in  an   eye  imposes  upon  its  accommodation   a 


iiviM:iv.\ii:rKt)i'i.\.  81 

constant  strain  to  maintain  distinct  vision.  It  has  been  found 
that  by  convergence  of  the  visual  axes  an  increase  in  the  power 
of  accommodation  will  be  gained,  and  the  greater  the  degree 
of  convergence  the  more  the  resulting  power  of  accommoda- 
tion. In  this  way  the  visual  lines  are  made  to  cross  each  other 
at  a  point  nearer  than  that  of  binocular  fixation,  and  while 
an  increase  in  the  force  of  acconuiiodation  is  thus  gained,  it  is 
at  the  expense  of  binocular  vision,  which  gives  way  to  diplopia 
or,  perhaps,  to  monocular  vision  because  the  image  cannot  be 
formed  on  the  yellow  spot  of  each  eye. 

The  visual  line  of  one  eye  fixes  the  object  looked  at,  and 
its  image  is  formed  on  the  yellow  spot,  while  the  visual  line 
of  the  other  eye  is  directed  to  another  point,  the  eye  itself  being 
placed  in  such  a  position  with  reference  to  the  object  fixed  by 
the  straight  eye,  that  its  image  is  formed  on  the  retina  at  a 
distance  from  the  yellow  spot.  These  two  images  therefore 
being  formed  on  parts  of  the  retina,  which  are  not  identical, 
cannot  be  fused  into  one,  and  double  vision  is  the  result. 

This  diplojiia,  while  ver\-  annoying  at  first,  does  not  last 
very  long,  for  the  following  reason:  the  image  of  the  object 
which  is  desired  to  be  seen  is  received  in  the  fixing  eye  and 
formed  on  the  most  sensitive  portion  of  its  retina,  and  hence 
the  impression  carried  to  the  brain  is  clear  and  distinct; 
whereas  the  corresponding  image  in  the  deviating  eye  is 
formed  on  a  portion  of  the  retina  which  is  much  less  sensitive, 
and  hence  the  impression  carried  to  the  brain  is  not  of  a  per- 
fect image. 

Under  such  circumstances  (in  cases  of  diplopia  where  one 
image  is  much  clearer  than  the  other)  the  sharp  image  of  the 
straight  eye  commands  of  the  brain  a  more  distinct  recogni- 
tion, which  is  only  disturbed  and  confused  by  the  feeble  im- 
pression received  from  the  squinting  eye,  and  hence  the  effort 
is  made  by  the  percipient  elements  to  suppress  the  recogni- 
tion of  the  latter  in  order  that  monocular  vision  may  be 
secured  and  prove  satisfactory. 

The  hypermetropic  child,  when  he  begins  to  use  his  eyes 
for  close  vision,  finds  that  he  cannot  see  distinctly  except  by 
a  considerable  effort,  of  which  he  is  conscious,  and  he  soon 
finds,  as  if  bv  instinct,  that  if  he  allows  one  eve  to  turn  inward 


82  HYl'KUMKTROriA. 

he  receives  a  clearer  image  in  the  other  eye,  and  with  less 
apparent  effort  of  accoinniodation.  Hence,  when  he  desires 
to  see  distinctly  at  a  close  range,  he  unconsciously  fixes  the 
object  with  one  eye,  while  the  visual  axis  of  the  other  eye  con- 
verges and  crosses  the  first  visual  line  at  a  point  nearer  than 
the  object. 

As  soon  as  the  gaze  is  removed  from  close  objects  and 
fixed  on  those  more  remote,  the  squint  disappears  and  the 
eyes  assume  their  normal  parallel  condition,  and  continue  so 
until  again  called  upon  to  adjust  the  vision  to  a  near  point, 
when  the  strabismus  returns.  The  natural  instinct  of  the 
child  (if  it  may  be  termed  such),  or  some  guiding  impulse, 
leads  the  child  to  prefer  clear  monocular  vision  to  blurred  or 
strained  binocular  vision. 

At  this  stage  the  squint  is  periodical,  manifesting  itself 
whenever  the  eyes  are  under  the  strain  of  close  vision  and 
vanishing  with  every  relaxation  of  the  accommodation.  With 
the  growth  of  the  child  and  his  advance  in  school,  the  eyes 
are  used  more  and  more  in  close  vision,  and  consequently  the 
condition  of  the  squint  is  present  for  a  greater  length  of  time, 
and  there  is  less  tendency  for  the  eyes  to  resume  their  normal 
position,  the  turning  inward  of  one  eye  lasting  even  after  the 
accommodation  is  passive,  until  finally  the  strabismus  becomes 
fixed  and  permanent  and  binocular  vision  is  forever  lost. 

IMPAIRMENT   OF   VISION    IN   THE    SQUINTING   EVE. 

In  some  cases  the  squint  appears  first  in  one  eye  and  then 
in  the  other,  and  under  such  conditions,  when  each  eye  shares 
alternately  in  the  act  of  vision,  the  sharpness  of  sight  is  equally 
retained  in  both  of  them.  But  it  usually  happens  that  one 
eye  is  preferred  for  vision  and  is  always  used,  and  then  the 
squinting  eye,  constantly  receiving  its  image  on  a  non-sensi- 
tive portion  of  the  retina  gradually  loses  its  powers  of  percep- 
tion and  its  acuteness  of  vision  is  very  much  impaired.  There 
may  be  no  organic  change  in  the  retina  that  can  be  detected 
by  the  ophthalmoscope,  but  from  non-participation  in  the  act 
of  vision  the  nervous  sensibility  becomes  blunted,  and  the  eye 
is  said  to  be  amblyopic. 


IIVI'KRMHTROPIA.  bJ 

If  an  operation  be  performed  early  and  the  muscular 
equilibrium  be  restored,  resulting-  in  a  return  of  binocular 
vision  and  the  action  of  the  two  eyes  in  harmony,  the  sensi- 
bility of  the  retina  may  again  be  raised  to  normal,  in  which 
case  it  may  become  necessary,  in  order  to  hasten  the  improve- 
ment, to  exclude  the  good  eye  and  exercise  the  other  for  a 
few  minutes  each  day  in  reading  with  a  convex  lens.  In  those 
cases  where  the  strabismus  has  lasted  for  many  years,  the  im- 
pairment of  vision  becomes  permanent,  and  no  operation  or 
any  amount  of  exercise  of  vision  will  avail  in  restoring  the 
sight. 

WHY    DOES    NOT    STKA15ISMUS    OCCUR    IX    EVERY    CASE    OF 
nYPERMETRGPIA? 

We  have  classed  convergent  strabismus  as  one  of  the 
evil  effects  ihat  may  result  from  hypermetropia,  but  in  read- 
ing the  rationale  of  its  production  the  query  may  logically 
arise  in  the  student's  mind,  why  does  not  strabismus  occur 
in  every  case  of  hypermetropia?  While  this  question  is  per- 
haps easier  asked  than  answered,  still  we  have  some  very  good 
reasons  for  its  non-occurrence  in  every  case. 

In  the  normal  eye  there  is  a  constant  natural  desire  for 
single  vision,  which  holds  equally  good  in  hypermetropia.  and 
it  becomes  the  duty  of  the  ocular  muscles  to  maintain  binocu- 
lar vision  if  at  all  possible.  This  results  in  a  struggle  between 
two  contending  impulses:  in  the  first  case  binocular  vision  is 
preserved  at  the  expense  of  clearness  of  sight;  in  the  second 
case  a  more  distinct  perception  is  enjoyed,  but  with  a  sacrifice 
of  single  vision.  In  the  former  condition  the  brain,  in  its 
abhorrence  of  double  vision,  strives  to  obtain  the  clearest  pos- 
sible image  and  still  retain  single  vision;  in  the  latter  predic- 
ament the  endeavor  to  secure  perfect  vision,  which  can  be 
accomplished  only  by  the  use  of  one  eye.  induces  the  brain  to 
suppress  the  image  formed  on  the  retina  (but  not  on  the  yel- 
low spot)  of  the  squinting  eye. 

In  this  contest  between  these  struggling  intluonces.  the 
abhorrence  of  double  images  and  the  desire  for  single  vision 
are  in  many  cases  the  most  powerful,  resulting  in  the  main- 
tenance   of    binocular    vision    and    the    prevention    of    squint. 


84  HVPERMETROriA. 

In  addition  to  this,  the  theory  has  been  advanced  that  some 
hypernietropes  may  pass  through  childhood  without  discover- 
ing tliat  they  are  able  to  secure  clear  and  distinct  images  by 
an  over-convergence;  but  this  proposition  \ve  are  not  alto- 
gether prepared  to  accept,  because  this  is  a  natural  instinct, 
and  on  account  of  the  close  relation  existing  between  accom- 
modation and  convergence  the  youthful  hypermetrope  will 
as  naturally  learn  to  increase  his  power  of  accommodation 
by  an  excessive  convergence,  as  he  will  to  use  his  legs  in 
walking. 

In  absolute  hypermetropia,  where  the  entire  refractive 
and  accommodative  power  of  the  eye,  even  when  assisted  by 
the  strongest  effort  of  convergence,  is  insufficient  to  form  a 
clear  image  on  the  retina,  there  is  no  motive  for  excessive 
convergence  because  there  is  nothing  to  be  gained  by  it,  and 
hence,  in  such  cases,  strabismus  is  not  likely  to  occur. 

PREVE-XTIOX    OF   STRABISMUS   BY   CONVEX   LENSES. 

Inasmuch  as  convergent  strabismus  is  one  of  the  results 
of  hypermetropia,  on  account  of  the  strain  imposed  upon  the 
accommodation,  it  naturally  follows  that  the  correction  of  the 
defect  and  the  removal  of  the  strain  would  be  an  important 
measure  of  preventive  treatment,  in  the  shape  of  properly 
adjusted  convex  lenses.  AMien  a  suggestion  of  this  kind  is 
made  to  the  mother  she  is  horrified  at  the  thought  of  her 
child  wearing  glasses;  and  if  perchance  her  scruples  are  over- 
come and  her  consent  given,  there  is  constant  difficulty  in 
coaxing  and  persuading  a  child  of  five  or  six  years  of  age  to 
wear  them. 

The  child  is  too  young  to  appreciate  the  useful  purpose 
for  which  they  are  given,  nor  is  he  inclined  to  accept  them  as 
playthings  given  for  his  amusement;  and  hence  they  do  not 
appeal  to  him  in  any  language  that  he  can  understand.  Con- 
sequently there  is  a  constant  strife  between  parent  and  child 
in  the  endeavor  to  control  the  inclination  of  the  latter  to  re- 
move the  glasses  and  to  prevent  their  being  broken.  After 
this  struggle  continues  for  a  while  the  parents  become  annoyed 
and  disgusted,  and  their  duty  in  this  respect  becomes  so  irk- 
some that  thev  neglect  it.  until  finallv  the  child  has  his  own 


IIVI'KRMKTRUPIA.  SO 

way,  the  glasses  are  laid  aside  and  lost,  and  the  periodic  squint 
becomes  permanent. 

OCCURKEXCE    OF    PERMANENT    STRABISNIUS. 

Even  after  the  squint  has  become  permanent,  the  duty  of 
the  parent  does  not  cease,  because  by  compelling  the  use  of  the 
eyes  in  alternation,  the  sight  of  both  may  be  kept  up  to  the 
normal  standard.  The  usual  tendency  is  for  the  child  to  use 
one  and  the  same  eye  constantly  for  all  purposes  of  virion, 
and  then  of  course  the  sight  of  the  other  eye  soon  deterior- 
ates. In  order  to  obviate  such  a  condition,  the  good  eye 
should  be  covered  with  a  handkerchief  or  a  light  bandage  for 
an  hour  or  two  each  day,  thus  compelling  a  use  of  the  squint- 
ing eye  and  maintaining  its  visual  powers  unimpaired. 

The  advantages  to  be  gained  from  such  a  practice  are 
obvious;  in  fact,  the  patient  retains  two  good  eyes  instead  of 
one,  and  in  such  a  case,  if  the  sight  of  one  is  impaired  or  lost 
by  injury  or  disease,  the  other  at  once  becomes  available  for 
immediate  and  satisfactory  use.  Also  if  an  operation  be  per- 
formed for  the  cure  of  the  strabismus  and  the  restoration  of 
the  natural  position  and  movements  of  the  eyes,  there  would 
be  much  more  hope  for  a  return  of  binocular  vision  if  both 
eyes  were  of  the  same  aeuteness  of  vision. 

PREVENTION  BETTER  THAN  CURE. 

However  the  prevention  of  the  periodic  squint  from  be- 
coming permanent  is  of  much  more  importance  to  the  child 
than  is  an  operation  for  its  cure,  for  it  is  very  doubtful  if  a 
strabismus  operation,  even  though  apparently  successful,  ever 
restores  the  ideal  singleness  of  vision  with  two  eyes — a  per- 
fect binocular  vision.  In  many  cases  this  is  most  likely  due 
to  the  fact  that  the  two  eyes  vary  in  their  acuteness  of  vision, 
and  this  fact  only  serves  to  emphasize  the  advice  given  above, 
that  the  attempt  should  always  be  made  to  keep  both  eyes  up 
to  the  normal  standard  by  alternating  their  use. 

The  occurrence  of  convergent  strabismus  in  a  child  just 
commencing  to  go  to  school  almost  certainly  indicates  the  ex- 
istence of  hypermetropia,  and  should  at  once  lead  to  a  careful 
and  skillful  examination  of  the  refraction,  in  order  that  the 


S6  iivim:kmi:tr(iima. 

defect  nui}-  he  (|uickl\  discovered  and  the  remedy  applied 
before  the  scpiint  hecoiiics  fixed;  because  strabismus  is  never 
due,  as  is  ])opularly  supposed,  to  fright,  imitation  or 
nauf^-htiness. 

The  statement  lias  been  made  b}-  some  authorities  that 
"the  greater  the  degree  of  hypermetropia  the  greater,  obvi- 
ously, is  its  tendency  to  produce  strabismus;''  and  while  on 
first  thought  this  seems  like  a  reasonable  assumption,  yet  it 
is  a  proposition  from  which  we  are  compelled  to  dissent.  In 
the  higher  degrees  of  hypermetropia,  where  the  accommoda- 
tion, with  all  the  added  assistance  of  convergence,  is  still  not 
strong  enough  to  overcome  the  refractive  error,  convergent 
strabismus  can  be  of  no  advantage  and  does  not  occur.  But 
it  is  in  the  moderate  degrees  of  the  defect  (from  2  D.  to  4  D.) 
that  the  accommodation  is  made  equal  to  the  task  of  neutral- 
izing the  defect  by  the  assistance  of  the  convergence,  and 
here  the  strabismus  is  most  commonly  found. 

The  theory  has  been  advanced  by  some  authors  that  the 
amblyopia  that  is  usually  found  in  a  squinting  eye  is  not  the 
result  of  the  strabismus,  but  is  the  cause  of  it.  They  argue 
that  the  defective  sensibility  of  the  retina  is  congenital  and 
thus  leads  to  the  production  of  strabismus;  but  they  are  able 
to  present  no  convincing  evidence  in  support  of  this  theory, 
and  the  opinion  of  the  writer  is  that  the  amblyopia  is  the  direct 
result  of  the  strabismus  as  explained  in  the  foregoing. 

9.       RETINITIS    AND    NEURITIS. 

Inflammations  of  the  retina  and  of  the  optic  nerve  are 
oftentimes  symptoms  of  grave  constitutional  diseases,  as 
syphilis  and  Bright's  disease,  and  yet  there  is  abundant  evi- 
dence to  prove  that  these  conditions  may  develop  in  patients 
who  are  entirely  free  from  such  maladies,  and  as  the  result 
of  over-use  of  the  eyes  or  the  strain  caused  by  hypermetropia; 
and  an  examination  of  a  large  number  of  cases  of  retinitis 
and  neuritis  has  shown  the  existence  of  hypermetropia  (per- 
haps in  a  latent  form)  in  a  great  majority  of  the  cases. 

Of  course  it  is  ciuite  possible  that  there  may  exist  in  these 
cases  some  underlying  constitutional  cause,  some  ])redisposi- 
tion   to   these   infiannnatory   conditions,   and    when    the   eyes 


Hvi'KRMirrRorrA.  87 

are  thus  rendered  susceptible,  it  re(|uires  but  a  little  strain  or 
a  trifling-  irritation  to  start  up  the  disease. 

lO.       XKKVorS  DKRAXGKMKNTS. 

The  strain  imposed  upon  the  eyes  by  an  uncorrected 
hvpernietropia  has  a  decided  effect  upon  the  nervous  system 
by  a  leakage  of  nerve  force,  and  may  lead  to  a  train  of  evils 
far  more  extended  that  we  are  accustomed  to  suppose.  \\'hen 
the  various  org-ans  of  the  body  perform  their  functions  har- 
moniously, each  receives  its  normal  supply  i>f  nerve  force,  and 
there  is  no  cause  for  irritation.  Hut  hypermetropia,  by  over- 
taxing the  ciliary  muscle  and  destroying  the  normal  relation 
that  should  exist  between  accommodation  and  convergence, 
calls  for  an  excessive  sup])ly  of  nervous  energy  and  acts  as 
an  irritant  to  the  central  nervous  system,  with  the  final  result 
of  a  breakdown  and  prostration  of  this  im])ortant  system, 
which  not  onlv  causes  misery  and  suffering,  but  statistics  are 
not  wanting  to  ])rove  that  the  duration  of  life  is  materially 
shortened  thereby. 

Chorea.  The  cHnical  experience  of  hospital  physicians 
has  demonstrated  most  positively  that  there  is  a  direct  relation- 
ship between  hypermetropia  and  chorea  or  St.  \'itus's  dance; 
the  percentage  of  this  defect  in  choreic  cases  being-  placed  as 
high  as  seventy  per  cent.  Therefore  it  follows  that  such  cases 
are  rapidly  cured  by  eye  treatment  alone,  the  correcting 
glasses  stopping  a  leakage  of  nervous  force  that  may  have 
been  going  on  for  years. 

Ef>ilc(^sy  is  one  of  the  most  terrible  diseases  that  can  befall 
any  human  being,  and  its  treatment  by  drug^s  alone  is  very 
unsatisfactory.  ( )f  late  years  specialists  on  nervous  diseases 
have  found  that  errors  of  refraction,  and  especially  hyperme- 
tropia. bear  a  direct  casual  relation  to  the  attacks,  and  that 
properly  adjusted  g-lasses  are  an  indispensable  a<ljuncl  to  the 
treatment,  if  they  do  not  even  supersede  all  other  methods  of 
treatment. 

Xcriviis  Prostration  ami  Insanity  are  very  closely  related, 
the  former  leading-  to  the  latter,  and  it  does  not  recpiire  any 
stretch  of  the  imagination  to  see  how  an  uncorrected  hyper- 
metropia, by  causing  a  leakage  and  excessive  expenditure  of 


b6  llVl'liRMJ-iTKul'lA. 

ner\-c   force,   may   develop  a  nervous   dehility    tliat    loads    \o 
niental  disturbance  and  ends  in  insanity. 

TESTS    FOR    IIY1'1':RM1-:TK01'IA, 

The  outfit  required  by  the  optician  for  use  in  refraction 
tests  lias  been  described  in  the  chapter  devoted  to  that  subject, 
and  a  rej^etition  of  the  ])araphcrnalia  sccnis  scarcely  necessary^ 
at  this  place;  but  their  use  and  the  methods  of  making-  the 
practical  tests  will  receive  a  detailed  description. 

The  various  tests  for  the  detection  and  determination  of 
hypermetropia  ma}-  be  enumerated  as  follows: 

1.  Trial  Case. 

2.  Skiascopy. 

3.  Ophthalmoscopy. 

4.  Chromatic  Test. 

5.  Scheiner's  Test. 

6.  Amplitude  of  Accommodation. 

THE    TKTAL    CASE. 

The  most  relialjle  test  for  hypermetro];ia,  antl  the  most 
satisfactory  on  which  to  rely  for  the  determination  of  the 
proper  glasses,  is  by  means  of  the  test  lenses  from  the  trial 
case.  The  improvement  of  distant  vision  l)y  convex  lenses, 
or  in  cases  of  normal  acuteness  of  vision  where  such  a  lens  is 
accepted  for  distance,  is  regarded  as  proof  positive  of  the  ex- 
istence of  hypermetropia.  iM-om  this  fact  it  does  not  follow 
that  the  acceptance  of  a  concave  lens  disproves  it,  as  fre- 
quently a  spasm  of  accommodation  is  an  accompaniment  of 
hypermetropia,  and  in  such  a  case  a  concave  lens  improves 
distant  vision  and  makes  the  case  apparently  myopic,  when  in 
fact  it  is  hypermetropic. 

ACt'TENESS   OF  VISIOX. 

The  first  step  in  the  examination  is  the  determination  of 
the  acuteness  of  visicw,  which  is  ascertained  by  means  of  tlK- 
test  card  hanging  twenty  feet  away.  This  may  equal  the  nor- 
mal standard  of  |[;,  or  it  may  fall  below  it.  The  degree  of 
acuteness  of  vision  present  does  not  throw  nnich  light  on  the 
existence  or  absence  of  hypermetropia. 


HVI'ERMETROPIA.  80 

li  ilic  visual  acuteiiess  is  |g.  the  uulv  certain  deduction 
that  can  be  drawn  is  that  the  case  is  not  one  of  myopia,  hut  it 
does  not  afford  any  information  as  to  the  presence  of  hyper- 
metropia,  because  a  normal  vision  may  mean  either  enuue- 
tropia  or  hypermetropia. 

On  the  other  hand,  if  the  vision  is  ^g,  or  ^{f,  or  l^,  the 
only  undisputed  inference  that  can  he  drawn  is  that  the  case 
is  not  one  of  emmetro'pia,  l)ut  there  is  no  knowledge  afforded 
as  to  the  existence  of  hvpermetro])ia,  because  a  lower  visual 
acuteness  ma\  mean  either  hypermetroi)ia.  myopia  or  astig- 
matism. 

COWKX   LEXSF.S  TIIK  TEST. 

How  then  is  the  j^resence  of  hypermetropia  to  be  deter- 
mined? I>y  the  acceptance  or  rejection  of  convex  lenses  for 
distant  vision.  A  weak  convex  lens  (usually  +  .50  D)  is 
placed  before  the  eye,  the  effect  of  which  at  once  becomes 
apparent,  one  way  or  the  other. 

If  the  acuteness  of  vision  is  fg,  and  this  convex  lens  blurs 
it,  it  is  fair  to  presume  that  the  eye  is  emmetropic:  but  if  the 
convex  lens  is  accepted,  that  is,  if  the  vision  remains  just  as 
good  with  the  lens  as  without  it,  and  if  the  No.  20  line  can  be 
just  as  clearly  read,  the  case  is  proven  to  be  one  of  hyperme- 
tropia. But  the  test  does  not  end  here,  as  the  refraction  has 
only  been  shown  to  be  hypermetropic,  the  degree  of  which 
may  be  much  greater  than  that  represented  by  the  -r  .50  D. 
lens.  A  +  .75  D.  lens  is  next  placed  in  the  trial  frame,  with 
which  the  No.  20  line  is  still  clearly  seen.  But  still  the  op- 
tician must  not  be  satisfied,  and  he  proceeds  to  use  the  next 
stronger  and  another  stronger,  continuing  as  long  as  the 
patient's  vision  remains  |5,  and  the  letters  on  this  line  are  dis- 
tinctly visible. 

Finally  a  lens  is  reached  that  causes  the  patient  to  shake 
his  head  and  say  the  letters  are  not  quite  as  plain  as  they  were 
before.  He  may  be  able  to  name  them,  because  he  has  prob- 
ably learned  them  by  heart  by  this  time,  but  he  is  conscious  of 
the  fact  that  their  sharpness  of  outline  is  less  marked,  and  some 
of  the  letters  he  is  doubtful  of.  What  has  been  determined 
now?     The  amount  of  the  manifest  hypermetrt^pia  has  been 


90  llVPKKMKTKdlMA. 

moasiircd,  l)y  jilaoiiii;'  sironiior  and  stroiii^-or  convex  lenses  in 
front  of  the  eye  imtil  the  vision  was  made  worse.  In  other 
words,  the  refraction  of  the  eye  was  increased  more  and  more 
by  the  addition  of  the  convex  lenses,  until  at  last  the  focus  of 
rays  of  light  was  formed  in  the  vitreous  humor  in  front  of  the 
retina,  whicli  sinudated  a  condition  of  niy<)])ia,  and  distant 
\ision  was  corresjjondingly  impaired. 

Jn  that  class  of  cases  where  the  vision  falls  below  f^,  the 
test  is  commenced  with  convex  lenses,  w'hich  are  not  only 
accepted,  but  cause  a  marked  improvement  in  vision.  A  + 
.50  D.  lens  is  tried  first,  and  at  once  the  patient  notices  that  the 
letters  are  clearer  and  blacker,  and  perhaps  he  is  enabled  to 
read  a  few  letters  on  the  next  line  below.  Then  a  -f  .75  lens 
is  tried,  and  a  +  1  D..  with  a  noticeable  improvement  each 
time,  and  still  stronger  lenses  until  the  acuteness  of  vision  is 
raised  to  ^JJ.  But  even  when  this  point  is  reached  the  test 
does  not  stop,  but  is  continued  by  the  addition  of  still  stronger 
lenses  imtil  the  No.  20  line  begins  to  be  dimmed.  Perhaps  a 
+  .50  D.  or  a  +  .75  D.  lens  stronger  will  be  accepted  than  that 
which  raises  vision  to  normal;  but  as  the  amount  of  defect  is 
not  measured  by  the  lens  that  first  makes  the  No.  20  line  read- 
able, but  by  the  strongest  lens  with  which  this  line  remains  so, 
the  test  is  not  ended  until  this  latter  lens  is  reached. 

NEVER  TRY  CONCAVE  LENSES  IN  HYPERMETROPIA. 

The  optician  should  be  cautioned  always  in  cases  of  sus- 
pected hypermetropia  to  commence  the  test  with  convex 
lenses,  and  if  they  improve  vision,  or  at  least  if  they  do  not 
make  it  worse,  the  refraction  is  proven  to  be  hypennetropic. 
Whereas  if  weak  concave  lenses  are  tried  first,  they  will  most 
likely  be  accepted  on  account  of  the  spasm  of  accommodation 
which  is  generally  present ;  and  when  once  accepted  they  serve 
to  stimulate  the  accommodation  to  still  further  contraction, 
and  then  if  convex  lenses  are  tried  afterward,  they  will  be 
promptly  rejected;  for  the  detection  of  hypermetropia  by 
means  of  convex  lenses  depends  upon  a  relaxation  of  the  ac- 
commodation to  the  extent  of  the  strength  of  the  convex  lenses 
used.     In  either  case  (with  or  without  convex  spherical  lenses) 


HVPERMETROPIA.  91 

the  rays  of  light  arc  l)rought  to  a  focus  at  tlie  same  i>lace,  and 
vision  remains  the  same. 

In  the  first  case  this  was  accomplislied  l)y  the  refractive 
power  supplied  by  the  crystalline  lens  of  the  eye,  and  in  tiic 
second  case  by  the  convex  lens  in  front  of  the  eye.  lUit  when 
concave  lenses  are  used  first  they  excite  the  accommodation 
and  cause  convex  lenses  to  be  rejected,  and  in  this  way  the 
diagnosis  of  the  case  becomes  doubtful,  and  the  optician  may 
he  led  into  serious  error. 

CAirioX    IX   CHANGIXG  THK    I.KNSKS. 

As  the  optician  changes  the  test-lenses  in  front  of  the  eye 
for  stronger  ones,  he  should  not  make  too  much  of  a  jump  or 
increase  their  strength  too  rapidly,  else  the  ciliary  muscle  con- 
tract spasmodically  and  he  fail  to  discover  the  hypermetroi)ia. 
But  he  should  increase  only  .25  D.  at  a  time,  leaving  each  lens 
in  front  of  the  eye  for  a  short  space  of  time,  thus  giving  the 
ciliary  muscle  an  opportunity  to  relax  and  encouraging  it  to 
do  so,  and  by  thus  chang-ing  the  lenses  slowly  and  increasing 
their  strength  gradually,  the  test  lenses  will  be  used  to  the 
greatest  jx^ssible  advantage  in  developing  and  detecting  hyper- 
metropia. 

THK  METHOD   BY  OVER-CORRECTIOX,  OR  THE  EOGGIXC.  SYSTEM. 

After  ascertaining  the  acuteness  of  vision,  a  strong  convex 
lens  is  at  once  placed  before  the  eye,  about  +  6  D.  in  ordinary 
cases,  or  even  stronger  if  there  is  reason  to  suspect  a  marked 
degree  of  hypermetropia.  Tliis  blurs  the  letters  on  the  dis- 
tance test  card,  and  the  patient  involuntarily  exclaims  that  he 
is  unable  to  see  with  it.  The  optician  encourages  him  to  look 
quietly  at  the  card  for  a  moment  or  two  without  straining 
his  eye,  and  after  the  eye  recovers  from  the  shock  of  suddenly 
placing  such  a  strong  lens  before  it,  the  vision  may  slightly 
improve. 

The  action  of  the  convex  lens  is  to  induce  a  relaxation 
of  the  accoinmodation,  as  only  in  this  way  can  the  vision  be 
made  even  slightly  better.  The  natural  tendency  for  the 
ciliary  muscle  is  to  contract,  but  a  contraction  of  this  muscle 
when  a  convex  lens  is  before  the  eve  instanth-  makes  vision 


i'V  IIVI-KKMI-  TKoriA. 

very  iiuu-h  worse.  'I'lic  eye  is  not  slow  to  appreciate  tliis  tact. 
aiul  then,  as  the  natural  instinct  of  the  eye  is  for  clear  vision, 
the  effort  is  made  in  the  other  direction,  that  is,  in  a  relaxation 
of  this  nuiscle,  which  at  once  tends  to  slig-htl\-  clear  the  vision. 
and  thus  a  further  relaxation  is  encourai^ed. 

Now  a  weak  concave  lens  ( —  .50  ]).)  is  ])laced  over  this 
convex  one,  and  by  diminishing-  its  strens.ith  improves  vision 
quite  noticeably  and  encourages  a  still  further  lessening  of 
acconuuodation.  After  this  lens  remains  a  l)rief  moment,  it  is 
replaced  by  a —  i  D.  lens,  wliicii  .-iffords  another  im])n)vement 
in  vision  and  enables  the  patient  to  see  more  of  the  letters. 
Then  —  1.50  D.  is  tried,  followed  by  —  2D.,  —  2.50  D.  and 

—  3  D.,  with  amelioration  of  vision  each  time  until  the  normal 
standard  is  reached,  and  then  the  difference  between  the  con- 
vex and  the  concave  lens  w^ill  be  the  measure  of  the  hyper- 
metropia. 

AN    ILLUSTRATION    OF   FOGGING. 

A  patient  presents  himself  with  all  the  smptoms  of  hyper- 
metropia  as  they  have  been  described  in  this  chapter.  On 
examination  his  acuteness  of  vision  is  found  to  be  |^.  Each 
eye  is  tested  separately  with  convex  lenses,  but  only  +  .50 
D.  is  accepted  and  a  stronger  lens  blurs  the  vision.  Then  the 
eyes  are  tried  together,  and  it  is  found  in  binocular  vision  that 
they  will  bear  +  i  D.,  but  nothing-  stronger. 

If  the  optician  desires  to  make  his  examination  thorough, 
he  wall  not  stop  here,  but  will  make  use  of  the  fogging  method. 
He  places  a  +  6  D.  lens  in  the  trial  frame,  with  which  the 
patient  is  unable  to  read  even  the  largest  letter  on  the  card 
at  first,  although  after  a  moment  he  may  be  able  to  discern 
the  form  of  the  No.  200  letter.  A  —  .50  D.  lens  is  then 
placed  in  the  front  groove  of  the  trial  frame,  which  renders 
this  letter  clear  and  easily  discerned.  Then  it  is  replaced  by 
a  —  I  D.  lens,  which  brings  out  the  No.  100  line.     Next,  a 

—  1.50  D.  lens  is  tried  with  the  effect  of  making-  clear  the  No. 
70  line  of  letters;  a  —  2D.  clears  up  the  No.  50  line,  a  — 
2.50  D.  the  No.  40,  and  a  —  3D.  brings  into  view  the  No. 
30  line,  and,  finally,  a  —  3.50  D.  brings  the  vision  up  to  |J 
clearly  and  distinctly. 


IIVPERMETROPIA.  93 

Now  what  lias  been  done  and  wliat  has  been  accom- 
plished? The  +  6  D.  lens  first  placed  before  the  eye  has  been 
partially  neutralized  by  the  —  3.50  D.  lens  and  reduced  to 
+  2.50  D.,  with  which  vision  is  Ig,  In  other  words,  the  eye 
has  been  led  to  accept  a  +  2.50  D.  lens,  with  w^hich  the  acute- 
ness  of  vision  is  unimpaired,  and  hence  this  is  the  measure  of 
the  defect. 

TEST   FOR  HYPERMETROPIA   BY   SKIASCOPY, 

The  essentials  for  the  test  by  skiascopy  are  a  darkened 
room,  a  bright  light  (either  electric,  gas  or  oil  will  answer), 
and  a  retinoscope,  to  which  may  be  added  the  trial  case. 

The  distance  of  the  optician  from  the  patient  is  a  matter  of 
considerable  interest,  for  which,  however,  there  is  no  fixed 
rule,  each  observer  within  certain  limits  selecting  his  own 
distance.  The  beginner  may  try  the  method  at  different  dis- 
tances, and  then  decide  for  himself  at  what  distance  he  obtains 
the  best  results.  When  the  plane  mirror  is  used  this  is  a  com- 
paratively simple  matter,  but  with  a  concave  mirror  any  great 
variation  in  the  distance  requires  a  corresponding  variation 
in  the  focus  of  the  mirror;  the  nearer  the  optician  approaches 
his  patient  the  shorter  should  be  the  focus  of  the  mirror,  and 
the  greater  the  distance  the  longer  the  focus. 

The  preference  of  the  writer  is  for  a  plane  mirror  and  a 
distance  of  one  meter,  the  advantages  of  this  distance  being 
that  it  is  close  enough  to  get  a  good  view  of  the  reflex  and 
shadow,  that  a  lens  can  be  placed  before  the  patient's  eye  and 
changed  at  will  without  requiring  the  optician  to  leave  his 
seat,  and  that  a  uniform  allowance  of  i  D.  is  thus  called  for 
in  the  estimate. 

-  The  light  should  be  steady,  clear  and  white,  and  as  bright 
as  possible;  the  Welsbach  light,  the  incandescent  electric  light 
or  an  Argand  burner  of  either  gas  or  oil  will  answer  the  pur- 
pose; and  in  order  to  obtain  the  brightest  part  of  the  flame,  it 
is  customary  to  use  an  asbestos  chimney  or  screen  with  an 
aperture  opposite  the  most  brilliant  part  of  the  flame. 

The  room  should  be  darkened  by  removing  all  sources 
of  light  except  the  one  in  use.     It  is  not  essential  that  the  ceil- 


94  HVPERMETROPIA. 

ing-  and  walls  of  the  room  should  be  black,  but  the  covering 
of  all  windows  by  black  shades,  that  fit  closely,  will  sufftce. 

The  positian  of  the  light  is  varied  by  different  authorities. 
Formerly,  the  advice  was  given  to  place  the  light  in  such  a 
position  above  the  head,  and  slightly  behind,  that  the  patient's 
eyes  will  be  in  the  shadow,  and  that  no  light  can  fall  on  the 
trial  lenses  that  may  be  placed  in  the  frame.  Or  the  light 
may  be  close  to  the  observer,  and  thence  reflected  on  the 
patient's  eyes,  the  optician's  eye,  the  light,  and  the  patient's 
eye  all  being  on  the  same  plane.  The  closer  the  light  is  to 
the  mirror,  the  brighter  will  be  the  reflected  rays. 


J  ^eter 


This  drawing  shows  the  mirror  at  a  distance  of  one  meter 
from  the  eye  under  examination,  and  the  darlv  lines  represent 
the  reflected  rays  from  the  mirror,  which  illuminate  the  retina, 
and  as  in  all  hypermetropic  eyes,  focus  behind  the  retina.  The 
dotted  lines  indicate  the  diverging  rays  proceeding  from  the 
retina,  and  the  convex  lens  of  3..50  D.,  which  is  placed  in  front 
of  the  eye.  and  which  possesses  just  sufficient  refractive  power 
to  bend  these  dotted  diverging  rays  and  bring  them  to  a  focus 
at  the  position  of  the  mirror  one  meter  away. 


METHOD   OF  CONDUCTING  THE  TEST. 

The  patient  and  optician  being  seated  at  the  proper  dis- 
tance, the  latter  takes  his  retinoscopic  mirror,  holds  it  in  front 
of  his  own  eye,  looks  through  the  sight  hole,  and  reflects  the 
light  on  the  patient's  pupil,  Avhich  at  once  appears  more  or 
less  brilliantly  illuminated,  according  to  the  condition  of  the 
refraction  of  the  eye,  and  the  portion  of  the  fundus  which  is 
being  observed. 

If  the  optic  disk  is  in  the  direct  line  of  view,  the  examina- 
tion is  more  easily  conducted;  but  as  the  refraction  at  the 
disk  may  possibly  vary  i  D.  or  even  2  D.  from  that  at  the 
macula,  the  latter  is  really  the  proper  part  of  the  fundus  to 


HVI'KRMKTROPIA.  95 

be  corrected,  to  obtain  wbich  the  patient  must  look  at  tlie 
sight-hole  of  the  mirror  during  the  whole  examination. 

The  reflection  from  the  eye  of  a  blonde  is  much  brighter 
than  from  a  brunette,  on  account  of  the  greater  amount  of 
pigment  in  the  eye-ground  of  the  latter.  The  reflection  is 
much  brighter  in  cases  of  low  refractive  error  than  in  high 
degrees  of  defect,  where  it  is  dull. 

The  sliadozu  is  the  dark  portion  of  the  retina  that  mi- 
mediately  surrounds  the  illumination;  they  adjoin  each  other, 
and  the  contrast  between  them  is  most  marked  and  more 
easily  recognized  when  the  illumination  is  the  brightest.  It 
is  this  combination  of  light  and  shadow  that  gives  the 
"shadow  test"  its  name.  In  a  darkened  room  the  retina  is  in 
darkness,  except  that  portion  which  is  illuminated  by  the  light 
from  the  mirror.  As  the  mirror  is  rotated,  the  retinal  illu- 
mination moves  and  shadow  takes  its  place.  It  is  this  change 
of  place  of  the  illumination  followed  by  the  shadow,  that 
causes  it  to  be  spoken  of  as  the  movement  of  the  shadow. 

As  the  mirror  is  slow-ly  and  slightly  rotated  first  one  way 
and  then  the  other,  around  an  imaginary  vertical  axis,  ihe 
light  reflection  moves  with  it  across  the  face  from  right  to 
left,  and  from  left  to  right.  Just  here  the  beginner  should 
know  that  the  illumination  of  the  patient's  face  alzivys  moves 
in  the  same  direction  as  the  mirror  is  rotated,  but  in  the  pupil- 
lary area  it  may  move  in  the  same  or  in  the  opposite  direction, 
as  it  is  aflfected  by  the  condition  of  the  refraction.  Hence 
when  the  movement  of  the  illumination  is  spoken  of.  it  is 
that  w^hich  is  seen  in  the  pupil  and  not  on  the  face. 

When  the  movement  of  the  retinal  illumination  is  tin- 
same  as  the  movement  of  the  light  on  the  patient's  face,  the 
case  is  presumably  one  of  emmetropia  or  hypermetropia,  in 
the  determination  of  which  convex  glasses  must  be  used  and 
placed  before  the  eye.  The  trial  frame  is  used  on  the  patient's 
face  with  a  -}-  i  D.  lens  over  the  eye  under  examination,  and 
the  light  is  again  reflected  on  the  pupil,  and  the  direction  of 
the  movement  is  again  observed.  If  this  lens  causes  the  light 
to  travel  in  a  direction  the  reverse  of  that  on  the  face,  the 
refraction  is  proven  to  be  emmetropic.  Whereas  if  the  shadow 
still  moves  in  the  same  direction  as  the  light,  the  eye  is  hyper- 


06  inrERMETKOl'JA. 

nietropic,  and  the  lens  must  be  changed  successively  for 
stronger  ones  until  finally  a  glass  is  reached  which  reverses 
the  movement. 

now    TO    MAKE    THE    NECESSARY    CALCULATIONS. 

\\'hcn  this  glass  is  found  it  is  compared  with  the  previous 
lens,  and  the  refraction  of  the  eye  is  between  the  two.  In  other 
words,  the  number  of  the  lens  is  found  between  the  weakest 
glass  which  reverses  the  movement  of  the  reflection  and  the 
strongest  glass  which  does  not  reverse  it.  If  when  a  +  3.25 
D.  lens  is  placed  in  the  trial  frame,  the  illumination  is  dimin- 
ished in  size  and  very  faint,  appears  to  move  rapidly  and  zvith 
the  light  on  the  face,  the  hypermetropia  is  still  slightly  un- 
corrected, and  a  stronger  lens  must  be  found.  If  a  +  3.75 
lens  is  substituted  for  it,  and  the  retinal  illumination  is  then 
found  to  move  opposite  to  the  movement  of  the  light  on  the 
face,  the  measure  of  the  defect  will  be  between  the  +  3.25  D. 
and  the  +  3.75  D.,  which  is  +  3.50  D. 

This  lens  has  converged  the  emergent  rays  issuing  from 
the  patient's  eye  and  brought  them  to  a  focus  in  the  optician's 
eye,  which  is  at  a  distance  of  one  meter;  and  in  so  doing  and 
fixing  the  far  point  at  one  meter,  it  has  practically  made 
the  eye  myopic  to  that  extent,  just  one  diopter.  Therefore 
when  the  patient's  vision  is  tested  with  the  letters  at  twenty 
feet,  this  i  D.  of  artificial  myopia  partly  neutralizes  the  3.50 
D.  of  hypermetropia,  and  the  result  of  adding  —  i  D.  to  -f- 
3.50  D.  gives  2.50  D.  as  the  amount  of  the  hypermetropia. 

This  -\-  2.50  D.  lens,  when  placed  before  a  hypermetropic 
eye,  suffices  to  render  parallel  the  divergent  rays  proceeding 
from  it,  and  conversely  would  so  refract  parallel  rays  of  light 
entering  the  eye,  as  to  exactly  focus  them  upon  the  retina. 
But  the  additional  +  i  D.  is  necessary  to  refract  the  emergent 
rays  still  more  in  order  to  bring  them  to  a  focus  at  one  meter. 

The  reader  who  follows  these  explanations  carefully  will 
readily  understand  why  the  correcting  glass  should  be  i  D. 
less  than  that  shown  by  the  retinoscope,  and  the  writer  de- 
sires to  draw  especial  attention  to  this  point,  as  it  is  one  that 
is  more  or  less  confused  in  the  mind  of  the  beginner  in 
retinoscopy. 


HYI'ERMETROPIA.  97 

TEST    FOR    IIVPERMKTROI'IA    15 V    THE    OrilTII ALMOSCf )rE. 

The  room  should  be  darkened,  and  the  same  light  can  be 
used  that  was  found  available  in  the  shadow  test.  It  should 
be  placed  (by  an  adjustable  bracket)  on  the  same  level  a:  the 
eye  that  is  to  be  examined,  and  on  the  same  side  of  the  head. 
Patient  and  optician  sit  facing-  each  other  and  side  by  side. 
The  pupil  is  then  illuminated  by  reflecting-  the  light  from  the 
concave  mirror,  and  the  red  reflex  is  obtained.  If  there  are 
any  opacities  in  any  of  the  refracting  media,  they  at  once  be- 
come apparent  by  marring  the  clearness  of  the  reflex. 

Presuming  there  are  none,  the  optician  at  once  passes  on 
to  the  direct  nwthod  of  the  use  of  the  ophthalmoscope,  which 
is  the  one  preferred  for  estimating  the  refraction.  This  gives 
an  upright,  enlarged  picture,  but  only  a  very  small  portion 
of  the  fundus  is  visible  at  one  time.  Tlie  optician  uses  his 
right  eye  to  examine  the  patient's  right,  and  approaches  as 
close  as  possible,  all  the  while  keeping  the  pupil  well  illumi- 
nated. The  beginner  finds  some  difficulty  in  keeping  the  light 
on  the  pupil  as  he  approaches,  and  as  soon  as  it  loses  its  bright 
red  reflex  he  may  know  he  is  at  fault  with  the  position  of  his 
mirror. 

In  an  emmetropic  eye,  parallel  rays  are  brought  to  a  focus 
exactly  on  the  retina  without  any  efifort  of  accommodation. 
Conversely,  the  rays  proceeding  from  the  retina  of  such  an  eye 
are  bent  by  its  refracting  media  in  such  a  way  as  to  issue 
from  the  eye  parallel. 

THE  OPTICAL  PRINCIPLES  INVOLVED  IN  THE  OPTHALMOSCOPIC 
TEST. 

In  hypermetropia  the  focus  of  parallel  rays  is  behind  the 
retina,  and  only  convergent  rays  can  be  focused  on  the  retina. 
As  no  such  rays  are  present  in  nature,  the  hypermetropic  eye 
is  adapted  for  a  condition  that  does  not  naturally  exist.  The 
rays  proceeding  from  the  retina  of  such  an  eye  are  bent  by  its 
refracting  media,  but  as  their  power  is  less  than  normal,  the 
rays  emerge  from  the  eye  divergent,  just  as  if  they  came  from 
a  point  behind  the  eye.  These  diverging  rays  can  be  rendered 
parallel  only  by  the  interposition  of  a  convex  lens  of  the  proper 
strength. 


98  HYPKRMKTROI'IA. 

If  the  eye  is  view  oil  through  the  ophthahiioscope  at  a  dis- 
tance of  twelve  or  fourteen  inches,  the  condition  of  the  re- 
fraction may  he  determined  by  the  appearance  and  behavior 
of  the  blood-vessels  as  they  are  seen  at  the  fundus  of  the  eve, 
that  is.  the  direction  in  whicli  they  will  travel  upon  the  moving 
of  the  head  of  the  observer. 

In  hypernietropia  a  more  or  less  clear  view  of  the  fundus 
can  be  obtained  at  this  distance  ^vith  the  mirror  alone.  The 
imag-e  is  enlarged,  erect  and  virtual,  and  as  the  optician  moves 
his  head  from  side  to  side,  the  disk  and  blood-vessels  will  seem 
to  move  in  the  stnuc  direction. 

In  emmetropia  the  optician  must  approach  much  closer  to 
the  observed  eye  in  order  to  get  a  distinct  view  of  the  disk  and 
vessels,  and  then  as  he  moves  his  head  their  behavior  will  be 
the  same  as  in  hypernietropia. 

The  power  of  accommodation  in  the  eyes  of  both  patient 
and  optician  is  supposed  to  be  at  rest.  In  order  to  favor  the 
relaxation  of  the  accommodation  in  the  i^atient's  eye,  the  room 
is  darkened  and  he  is  requested  to  turn  his  eyes  in  a  distant 
direction,  without,  however,  endeavoring  to  fix  any  one  par- 
ticular object  in  distinct  vision.  For  the  optician  it  is  some- 
times a  difificult  matter  to  place  the  accommodation  at  rest, 
because,  in  looking  at  the  fundus  of  the  patient's  eye,  he  is 
inclined  to  adjust  his  accommodation  as  for  a  near  object; 
whereas  he  should  endeavor  to  relax  his  eye  and  place  it  in  the 
condition  for  viewing  distant  objects.  If  the  fundus  be  viewed 
as  at  a  near  point,  the  amount  of  accommodation  brought  into 
play  will  render  the  optician's  eye  practically  myopic,  and  this 
is  the  reason  why  so  many  beginners  can  get  a  clearer  view 
of  the  eye-ground  by  rotating  a  weak  concave  lens  in  the  sight- 
hole  of  the  ophthalmoscope.  Therefore,  it  should  be  borne 
in  mind  that  the  improvement  caused  by  a  concave  lens  must 
not  be  considered  as  proof  positive  of  the  existence  of  my- 
opia. 

RELAXATION    OF    THE    ACCOMMODATIOX. 

The  power  to  completely  relax  his  ciliary  muscle  is  a 
faculty  that  should  be  cultivated  by  the  ophthalmoscopist;  and 
as  it  is  so  essential  in  the  determination  of  hypernietropia,  the 


HYPERMETROPIA. 


09 


following  procedures  will  be  found  of  benefit  in  assisting  to 
that  end. 

The  optician  looks  ui)wanl  and  at  the  same  time  holds 
above  his  eyes  a  white  card  on  which  there  is  a  black  spot. 
He  then  endeavors  to  relax  his  accommodation,  and  as  soon 
as  he  succeeds  the  sjiot  will  appear  double;  then  the  card  is 
to  be  lowered,  the  e>es  following  it,  and  as  long  as  the  spot 
continues  to  appear  double  he  will  know  that  his  accommoda- 
tion is  at  rest. 

Another  exercise  which  is  adapted  for  the  same  purpose, 
is  to  hold  a  pen  or  pencil  about  ten  inches  in  front  of  the  face, 
and  if  the  ciliary  muscle  can  be  relaxed  and  the  vision  adjusted 
for  distance,  the  pencil  will  appear  double,  and  will  continue 
so  as  long  as  the  ciliary  muscle  can  be  kept  quiescent. 

Still  another  method  of  practicing  the  same  thing  is  to 
hold  a  book  as  close  to  the  eyes  as  possible ;  then  the  observer 
is  to  commence  to  read,  and  while  thus  engaged  he  endeavors 
to  look  through  the  book  or  beyond  it,  when  the  letters  will 
run  together  and  become  obscured,  because  when  the  accom- 
modation relaxes  the  letters  are  no  longer  focused  upon  the 
retina;  at  the  same  time  the  optician  will  probably  feel  that  the 
act  of  convergence  lessens  and  the  eyes  gradually  turn  out- 
w^ard  until  their  visual  axes  assume  a  parallel  position. 

By  a  frequent  repetition  of  one  or  all  of  the  above  exer- 
cises, the  beginner  can  learn  to  approximate  an  object  close 
to  his  eyes,  and  at  the  same  time  keep  his  acconmiodation  and 
convergence  in  abeyance.  Having  thus  secured  control  of 
his  accommodation,  the  optician  will  be  in  a  position  to  esti- 
mate by  the  use  of  the  ophthalmoscope  the  amount  of  hyper- 
metropia  in  any  particular  case. 

WHAT  TO  LOOK  FOR. 

The  optician  should  familiarize  himself  with  the  appear- 
ance of  the  normal  fundus;  first  by  a  careful  study  of  the 
colored  plate  given  in  a  previous  chapter,  and  then  by  actual 
use  of  the  ophthalmoscope  with  healthy  eyes.  The  optic  disk, 
that  is.  the  entrance  of  the  optic  nerve,  is  the  object  to  be 
looked  for.  it  being  circular  in  shape  and  much  lighter  than 
the  retina,  which  presents  a  bright,  rose-red,  granular  appear- 


100  HYPERMETROPIA. 

ance.  In  brunettes  there  is  more  pigment  matter  in  the  retina, 
which  brings  out  in  strong  contrast  the  difference  in  color 
of  the  disk  and  the  retina. 

The  optician  now  endeavors  to  get  a  clear  view  of  the 
details  of  the  fundus,  and  if  he  and  his  patient  are  both  em- 
metropic this  is  a  comparatively  simple  matter.  If  the 
observer  is  not  emmetropic,  he  must  wear  his  correcting 
glasses.  If  he  looks  into  an  hypermetropic  eye  (of  moderate 
degree)  he  will  again  see  the  features  of  the  eye-ground  clearly 
and  distinctly,  but  by  the  involuntary  use  of  his  accommoda- 
tion. A  distinct  picture  being  thus  obtained  in  both  emme- 
tropia  and  hypermetropia,  how  can  it  be  determined  which 
condition  is  present?  By  the  revolving  of  a  convex  lens  into 
the  sight-hole  of  the  ophthalmoscope,  and  if  the  picture  still 
continues  as  clear  (or  is  made  more  distinct)  the  case  is  known 
to  be  one  of  hypermetropia.  And  the  strongest  convex  lens 
with  which  the  optician  can  get  a  clear  view  of  the  optic  disk 
and  the  blood-vessels  will  be  the  measure  of  the  defect,  pre- 
suming that  both  persons  have  been  able  to  relax  their  ciliary 
muscles. 

In  order  to  insure  an  exact  measurement  of  the  patient's 
refraction  by  means  of  the  ophthalmoscope,  the  advice  is  given 
by  some  authorities  to  use  the  region  of  the  yellow  spot  for 
the  examination.  But  unless  the  eye  is  under  the  influence 
of  a. mydriatic,  this  is  a  difficult  matter,  because  the  pupil 
sharply  contracts  as  soon  as  the  yellow  spot  turns  toward  the 
mirror;  and  besides  there  is  no  marked  feature  here;  such  as  a 
blood-vessel,  which  can  be  used  for  accurate  focusing. 

For  all  practical  purposes  the  optic  disk  will  be  entirely 
satisfactory  for  this  examination,  and  preferably  the  side  of 
the  disk  toward  the  temple,  because  its  margin  here  is  gener- 
ally well  defined.  The  small  blood-vessels  as  they  pass  over 
the  edge  of  the  disk  are  to  be  observed;  this  makes  a  delicate 
test,  as  the  variation  of  but  a  fraction  of  a  dioptric  is  sufficient 
to  throw  them  in  or  out  of  focus. 

Tlie  optic  disk  is  seen  if  the  patient  turns  his  eye  slightly 
inward  toward  the  nose,  while  the  yellow  spot  comes  into 
view  when  he  looks  directly  at  the  hole  in  the  mirror,  while 
the  course  of  the  main  retinal  vessels  can  be  traced  by  the 


HYPERMETROPIA. 


101 


optician  moving-  his  head,  and  directing  the  patient  to  turn  his 
eye,  in  an  appropriate  direction  as  the  course  of  each  vessel  is 
being  followed. 

CHROMATIC   TEST    FOR   IIVPERMETROPI A. 

This  test  has  been  fully  described  and  illustrated  with 
colored  plates  in  the  chapter  on  "Method  of  Examination." 
It  is  a  ready  and  convenient  test  for  detecting  hypermetropia, 
in  which  defect  the  retina,  being  farther  front  than  normal, 
approaches  the  focus  of  the  blue  rays,  causing  the  flame  to 
appear  wath  a  blue  center  and  a  red  border.  Tlie  convex  lens 
that  neutralizes  the  flame  and  fuses  it  into  a  single  color  will 
be  the  measure  of  the  defect. 


In  this  illustration  the  rays  are  shown  which  emanate 
from  the  candle  flame  and  pass  through  the  perforations 
in  the  card,  and,  being  bent  by  the  refracting  media  of 
the  eye,  are  focused  on  the  retina  of  the  emmetropic  eye. 
which  is  shown  by  the  dotted  lines.  The  hypermetropic 
eye  being  flatter,  its  retina  is  farther  forward,  as  shown 
by  the  black  line,  and  the  rays  striking  it  before  their 
union  produce  there  two  images  of  the  flame,  and  there- 
fore to  such  a  person  the  flame  is  seen  double. 


SCIIEIXERS   TEST. 

This  test  for  hypermetropia  is  one  that  is  not  in  common 
use,  and  yet  it  illustrates  so  beautifully  certain  optical  princi- 
ples that  it  is  desirable  the  optician  should  be  familiar  with  it. 
A  card  with  two  small  holes,  so  close  together  that  rays  passing 
through  them  will  enter  the  pupil,  is  placed  in  front  of  the  eye 
to  be  examined.  Tlie  patient  looks  through  these  holes  at  a 
candle  flame  twenty  feet  away,  and  if  the  eye  is  hypermetropic 
two  flames  are  seen,  instead  of  one  as  in  emmetropia. 

The  explanation  of  this  phenomenon  is  as  follows:  the 
rays  of  light  proceeding  from  the  candle  flame  travel  in  all 
directions   and   fall   upon    the   card,   a   few   of   them   passing 


102  HYPERMKTROriA. 

through  the  pcrkirations;  ami  if  the  eye  is  adapted  to  the  llanie, 
that  is,  if  it  be  eiiinietro])ic.  these  two  sets  of  rays  will  exactly 
meet  on  the  retina,  and  form  there  a  single  image  of  the  flame. 
If,  however,  the  eye  be  hypermetropic  and  the  defect  be 
not  corrected  by  the  accommodation,  the  two  sets  of  rays  will 
strike  the  retina  before  they  have  had  the  opportunity  to  meet, 
and  each  set  will  form  an  image  of  the  flame.  Tlie  greater  the 
degree  of  the  hypermetropia,  the  farther  apart  the  two  images 
will  be.  Convex  lenses  are  then  taken  from  the  trial  case  and 
placed  between  the  card  and  the  eye,  and  that  convex  lens 
which  causes  the  flame  to  be  seen  singly  will  be  the  measure  of 
the  defect. 

DETECTION    OF    HYPERMETROPIA    BY    MEASURING    THE    AMPLI- 
TUDE OF  ACCOMMODATION. 

The  amplitude  of  accommodation  is  the  power  exerted  by 
the  eye  to  change  its  adjustment  from  a  far  point  to  the  near 
point,  and  is  measured  by  the  closest  point  at  which  the  patient 
is  able  to  read  the  fine  print.  The  lens  whose  refractive  power 
corresponds  to  this  focal  distance  will  represent  the  amplitude 
of  accommodation. 

For  instance,  if  twenty  inches  is  found  to  be  the  distance 
of  the  near  point,  the  amplitude  of  accommodation  would  be 
2  D.  If  the  near  point  is  thirteen  inches,  the  accommodation 
is  equal  to  a  lens  of  3  D.;  and  if  the  near  point  is  ten  inches, 
the  accommodation  is  4  D. 

In  emmetropia  the  amount  of  amplitude  of  accommoda- 
tion is  a  constant  one  for  the  different  ages  all  through  life,  as 
shown  by  the  following  table: 


'ears. 

Amplitude  of 

Years. 

Amplitude  of 

Accommodation. 

Accommodation. 

10 

14  D. 

40 

4.50  D. 

15 

12  D. 

45 

3.50  D. 

20 

10  D. 

50 

2.50  D. 

2.5 

OD. 

55 

1.50  D. 

30 

7  n. 

60 

.50  D. 

35 

OD. 

This  is  the  standard  by  which  every  case  must  be  gauged, 
and  any  departure  from  which,  at  any  certain  age,  can  be 
readily  detected. 

A  hypermetropic  eye  requires  some  of  its  accommoda- 
tion for  distant  vision,  and  hence  for  close  use  there  is  a  de- 


HYPERMKTROPIA.  103 

ficiency  of  that  aiiioinil ;  tliorcforc  the  ani])HtU(le  of  accom- 
modation present  in  a  hypermetropic  eye  at  a  s^iven  age 
would  be  less  than  is  indicated  in  the  table  for  the  same  age; 
and  the  amount  by  which  it  is  less  would  indicate  the  degree  of 
defect. 

l*'or  instance,  if  on  examination  a  patient  thirty  }ears  of 
age  has  a  near  point  of  eight  inches,  representing  an  ampli- 
tude of  accommodation  of  5  !).,  it  is  at  once  evident  there  is 
a  deficiency  of  2  D.,  and  a  presumi)tion  of  the  existence  of  a 
hypermetropia  of  that  amount. 

A\'ith  the  same  amplitude  of  acconnnodation  it  is  evident 
that  the  near  point  is  farther  away  in  hypermetropia  than  in 
emmetropia.  as  is  shown  in  the  above  instance,  where  the  near 
point  is  at  eight  inches  instead  of  five  and  a  half  inches,  the 
normal  distance.  In  this  way  the  existence  of  a  latent  hyper- 
metropia can  often  be  determined,  that  could  not.  iK'rhaps,  be 
detected  by  the  usual  test  with  trial  lenses. 

TIIK    TKSTS     FOR     1 1  V  I'KKM  ETROIM  A    CO.MPAKEI). 

In  considering  the  value  of  the  tests  that  have  been  de- 
scribed for  the  determination  of  hypermetropia,  the  optician 
soon  discovers  that  the  two  objective  tests  (ophthalmoscopy 
and  retinoscopy)  are  somewhat  difificult  to  learn.  Of  course 
he  knows  that  the  theories  involved  and  phenomena  observed 
are  simple  and  easily  understood,  but  it  requires  much  time 
and  practice  to  become  an  expert  in  the  use  of  these  methods. 
Therefore  they  may  be  considered  subordinate  to  the  test  by 
the  trial  lenses,  which  is  really  the  decisive  one.  And  then, 
finally,  even  this  test  yields  to  that  which  is  given  by  the 
patient  himself  when  he  commences  to  wear  the  glasses  which 
have  been  ordered. 

REMARKAHLE   ACUTEXKSS    OF    VISION    IX    II VPERMETROPI A. 

In  a  description  of  this  defect  of  hypermetropia  it  should 
be  noted  that  hypermetropic  eyes  sometimes  enjo\-  an  un- 
usual degree  of  aeuteness  of  sight,  and,  in  fact,  when  young, 
they  are  very  ai)t  to  boast  of  their  power  of  vision.  They  can- 
not only  read  all  the  No.  20  line  without  an  error  when  seated 
at  twentv  feet  but  will  also  call  ofif  the  letters  on  the  next  line 


104  HYPERMETROPIA. 

c|uitc  as  readily.  The  parents  of  such  a  boy  will  tell  how  the 
child  can  see  things  with  an  ease  and  distinctness  which  thev 
themselves  do  not  possess.  They  may  laugh  at  the  suggestion 
of  any  defect  in  the  eyes  of  their  child,  and  ridicule  the  thought 
of  glasses  as  long  as  the  child  can  get  along  without  them. 

I'REJUDICE  AGAINST  GLASSES. 

There  is  no  use  denying  the  universal  prejudice  that  has 
existed  in  the  public  mind,  but  which,  fortunately,  is  not  so 
pronounced  now  as  formerly  that  glasses  are  an  injury  when 
they  can  be  avoided  for  fear  the  patient  may  become  so  de- 
pendent upon  them  as  never  to  be  able  to  remove  them.  This 
is  certainly  not  good  grounds  for  an  argument,  but  the  proper 
light  in  which  the  matter  should  be  viewed  is  that  if  Nature 
is  dependent  upon  a  glass  w^iich  affords  relief  and  removes 
strain,  such  means  of  assistance  should  not  be  withheld. 

If  the  pain  in  hip  disease  is  arrested  by  a  properly- 
adapted  support,  should  the  splint  be  denied  the  patient  be- 
cause he  feels  his  dependence  upon  it?  Is  there  any  more 
reason  why  a  patient  with  defective  eyes  should  go  through 
life  without  the  relief  that  glasses  only  can  afford,  simply 
because  of  unfounded  prejudice  against  their  use? 

A  case  is  related  of  a  physician  who  refused  to  allow  an 
oculist  to  examine  his  children's  eyes,  with  the  statement  that 
no  child  of  his  should  ever  wear  glasses  with  his  consent.  The 
children  suffered  from  weekly  attacks  of  sick  headaches,  and 
finally  one  w^as  fitted  with  a  +  3.25  D.  lens,  another  with  the 
same  sphere  combined  with  5°  prisms,  and  the  third  was  also 
highly  hypermetropic  and  astigmatic.  Immediate  relief  was 
afforded  in  each  one  of  these  cases  by  the  correction  of  an 
optical  defect  which  had  rendered  their  early  life  one  of  suf- 
fering. This  is  not  an  uncommon  experience  w'ith  oculists 
and  opticians. 

SICK   HEADACHES. 

There  is  every  reason  to  believe  that  there  are  thousands 
of  sufferers  from  sick  headache  who  are  struggling  through 
life  with  an  uncorrected  hypermetropia,  who  have  made  un- 
successful efforts  for  relief  at  the  hands  of  doctors  and  drugs. 
and  who  have  in  despair  abandoned  all  hope  of  cure.     This 


HYPERMETROPIA.  105 

is  an  interesting  study  for  the  ambitious  optician,  and  forms 
a  wide  and  promising  field  for  the  exercise  of  his  skill  and 
judgment. 

The  statement  is  made  by  eminent  authorities  that  the 
gastric  symptoms  which  accompany  typical  attacks  of  sick 
headache  are  not  due  to  "biliousness,"  or  "disordered  liver," 
or  "dyspeptic  conditions,"  or  "the  use  of  tobacco  to  excess," 
or  "living  too  high,"  but  they  are  reflex  in  character,  and,  in 
the  majority  of  cases,  due  to  hypermetropia.  These  attacks 
often  occur  without  any  explainable  cause,  and  they  are 
sometimes  even  cured  by  eating,  drinking  or  smoking,  while 
at  other  times  they  are  aggravated  by  similar  indulgences. 
Every  known  remedy  in  the  pharmacopoeia  has  been  tried, 
at  first  with  success,  acting  almost  as  specifics,  and  later  prov- 
ing entirely  valueless,  until  finally  life  is  rendered  really  un- 
endurable. 

The  brain  and  central  nervous  system  preside  over  all 
the  functions  of  life.  If  now^  this  ruling  spirit  is  disturbed  by 
the  irritation  caused  by  a  constant  strain  to  use  the  eyes  in 
the  face  of  an  uncorrected  hypermetropia,  may  not  this  dis- 
turbance manifest  itself  by  an  interference  with  the  normal 
functions,  as  shown  by  nausea,  vomiting,  dizziness,  and  other 
evidences  of  impaired  animal  life?  This  reasoning  is  plausi- 
ble, and  although  they  are  the  views  of  an  extremist,  they 
contain  much  of  truth,  and  suggest  a  train  of  thought  and 
experiment  that  can  be  successfully  carried  out  by  every  in- 
telligent optician. 

RECAPITULATORY    REMARKS. 

Before  concluding  this  chapter  on  hypermetropia.  at  the 
risk  of  possible  repetition  it  seems  desirable  to  mention  again 
a  few  of  the  important  points  that  should  be  borne  in  mind 
in  adjusting  glasses  for  the  correction  of  this  defect. 

In  obtaining  the  liistory  of  the  case  the  optician  should 
ascertain  whether  or  not  the  patient  has  been  wearing  glasses, 
and  if  so,  what  kind,  what  number,  and  how  long.  Even 
though  they  are  entirely  unsuitable,  they  may  serve  as  a 
guide  in  making  the  test  and  prevent  the  prescription  of  sim- 
ilar glasses,  which  the  optician  might  be  led  to  give  if  he  was 
not  thus  warned. 


lOG  HYPERMETROPIA. 

In  testing^  the  vision  at  twenty  feet,  every  letter  in  the  No. 
20  line  may  seem  black  and  the  outlines  of  the  letters  clearly 
(Jetined.  and  the  i)resumption  would  be  that  the  patient  was 
emmetropic,  hut  he  ////_<f///  be  hypermetropic;  the  determination 
of  which  depends  (m  the  acceptance  or  rejection  of  a  convex 
lens.  A  weak  lens  is  used  (generally  +  .50  D.),  and  if  the 
patient  rejects  this  it  is  reasonable  to  infer  there  is  no  hyper- 
metropia  present  (barring  those  cases  of  latent  defect,  which 
do  not  enter  into  our  consideration  now). 

If.  on  the  other  hand,  this  convex  lens  is  accepted,  it  is 
fair  to  assume  the  case  is  one  of  hypermetropia.  Then  a 
stronger  one  is  tried,  and  still  a  stronger,  the  patient  all  the 
while  looking  at  the  No.  20  line,  until  he  says  the  letters  are 
slightly  dimmed  or  less  distinctly  seen.  This  lens  is  then  to 
be  compared  with  the  previous  one  and  with  several  weaker 
and  stronger,  until  finally  the  one  chosen  is  the  strongest 
that  afifords  the  best  vision.  If  the  degree  of  defect  is  found 
to  be  considerable,  the  lenses  may  be  increased  .50  D.  at  a 
time,  but  ordinarily  the  better  plan  is  to  change  only  .25  D., 
and  thus  allow-  the  accommodation  to  gradually  adapt  itself 
to  the  convex  lenses. 

It  is  customary  to  fit  one  eye  at  a  time,  but  this  monocu- 
lar vision  is  never  as  satisfactory  with  either  eye  as  is  binocu- 
lar vision,  and,  in  fact,  if  there  is  not  much  difference  in  the 
acuteness  of  vision  of  the  two  eyes  they  may  be  tried  to- 
gether, when  a  stronger  lens  will  usually  be  accepted.  When 
the  refractive  power  of  the  eyes  varies  so  much  as  tO'  produce 
discomfort,  then  they  must  be  measured  separately  and  the 
best  eye  accurately  fitted,  and  an  approximate  correction 
given  to  the  other  eye,  not  allowing  a  great  enough  differ- 
ence between  the  lenses  to  cause  discomfort.  In  these  lat- 
ter cases  the  eyes  will  gradually  accustom  themselves  to  the 
glasses,  so  that  in  time  a  much  greater  difiference  will  be  borne 
than  at  first  seemed  possible. 

When  presbyopia  begins  to  steal  over  the  hypermetropic 
eye,  as  it  does  earlier  in  life  than  normal,  and  the  accommo- 
dation becomes  unequal  for  reading  and  fine  work,  two  pairs 
of  glasses  are  required,  the  new  and  stronger  glasses  for  close 
use.  while  the  old  and  weaker  glasses  w'hich  the  patient  has 


HYPERMKTROPIA.  107 

been  wearing  for  his  hypernietropia,  and  to  which  his  eyes 
have  become  accustonied,  remain  good  for  distance.  A  per- 
son with  a  hypernietropia  of  2  I),  and  wearing  glasses  of  that 
strength  to  correct  it,  would,  in  the  ordinary  course  of  events, 
at  the  age  of  forty-five  years  have  a  presbyopia  of  aljout  i 
D.;  such  a  person  would  therefore  need  +  3  D.  for  reading, 
and  continue  to  wear  his  +  2  D.  for  distance. 

ARTIFICIAL    IIVl'KKMETKOriA,    OR    Al'IIAKIA. 

Aphakia  is  the  term  used  to  represent  that  condition  of 
the  eye  in  which  the  crystalline  lens  is  absent  from  its  posi- 
tion in  the  center  of  the  pupil.  This  may  result  from  luxation 
of  the  lens  and  its  removal  from  the  plane  of  vision,  or  if  the 
capsule  of  the  lens  be  punctured  or  ruptured  its  substance 
may  be  dissolved  in  the  aqueous  humor  and  removed  by 
absorption. 

By  far  the  most  frequent  cause,  however,  for  the  absence 
of  the  lens  is  its  extraction  from  the  eye  by  one  of  the  various 
operations  for  cataract.  Inasmuch  as  the  crystalline  lens  is 
the  principal  refracting  medium  of  the  eye,  its  removal  leaves 
the  eye  intensely  hypermetropic  and  destitute  of  all  accom- 
modative power;  it  is  in  a  state  of  absolute  hypernietropia. 
It  has  been  conclusively  proven  that  in  the  absence  of  the 
crystalline  lens  there  remains  not  the  slightest  trace  of  accom- 
modation. This  fact  establishes  the  correctness  of  the  uni- 
versally adopted  theory  (if,  indeed,  it  needs  any  corrobora- 
tion) that  the  power  of  adjusting  the  dioptric  apparatus  of 
the  eye  for  close  vision  depends  entirely  upon  changes  in  the 
convexity  of  the  crystalline  lens. 

In  chapter  \T.  of  this  work  on  The  Physiology  of 
\'ision  will  be  found  an  illustration  of  candle-flame  images 
in  the  eye,  three  in  number,  the  first  being  erect  and  reflected 
from  the  cornea,  the  second,  also  upright,  is  formed  on  the 
anterior  convex  surface  of  the  crystalline  lens,  and  the  third 
is  inverted  and  reflected  from  the  posterior  concave  surface 
of  the  lens.  When  the  flame  is  moved  up  and  down,  the  two 
erect  images  move  with  it  and  the  inverted  one  in  an  oppo- 
site direction.    In  a])hakia  there  remains  onl\  the  sinij;le  image 


108  HVPERMETKOl'IA. 

on  the  cornea,  the  two  reflected  from  the  surface  of  the  lens 
being:  absent. 

The  eye  being  left  in  a  condition  of  absolute  hyperme- 
tropia,  it  becomes  necessary  to  measure  its  degree,  which  can 
be  readily  accomplished  by  means  of  the  test  by  trial  lenses. 
Strong  convex  lenses  will  be  required  to  take  the  place  of 
the  absent  lens,  the  strength  of  which  will,  of  course,  be  in- 
fluenced by  the  previous  condition  of  the  refraction  of  the 
eye;  if  formerly  hypermetropic,  stronger  glasses  will  be  called 
for,  and  if  myopic,  weaker  convexes  will  suffice. 

If  the  degree  of  myopia  was  as  high  as  lo  D.  or  more, 
its  aphakial  condition  might  readily  be  one  of  emmetropia. 

When  the  crystalline  lens  is  removed  from  an  emmetropic 
eye,  the  glass  that  is  needed  to  take  its  place  and  bring  parallel 
rays  to  a  focus  on  the  retina  is  usually  about  +  lo  D.,  some- 
times a  little  stronger.  On  account  of  the  absence  of  all 
accommodation,  stronger  glasses  will,  of  course,  be  required 
to  focus  on  the  retina  the  divergent  rays  proceeding  from  near 
objects.  In  order  to  determine  the  proper  glass  for  reading, 
we  add  to  the  first  glass  one  whose  focus  represents  the  dis- 
tance at  which  the  patient  wishes  to  read.  For  instance,  if 
ID  D.  was  found  to  be  the  proper  lens  for  distance,  and  ten 
inches  was  decided  on  as  the  desired  point  for  reading;  then 
the  latter,  which  equals  4  D.,  is  added  to  the  former,  and  the 
result  is  a  lens  of  +  14  D.  for  reading. 

An  artificial  accommodation  may  be  produced  by  a  change 
in  the  distance  of  the  spectacles  from  the  eyes,  thus  adapting 
them  for  intermediate  points,  on  the  principle  that  as  the  spec- 
tacles are  moved  farther  away  down  the  nose,  their  refractive 
power  is  increased  and  the  reading  point  is  brought  nearer, 
while  as  they  are  pushed  up  close  to  the  eyes  their  power  is 
lessened  and  the  reading  point  is  moved  away. 

APHAKIAL    VISION. 

In  addition  to  the  hypermetropic  refraction  caused  by  the 
removal  of  the  crystalline  lens,  a  certain  degree  of  astigmatism 
is  also  the  result  of  the  operation,  most  likely  due  to  failure  of 
the  wound  to  heal  properly.  This  astigmatism  is  generally 
"against  the  rule,"  and  is  apt  to  be  more  noticeable  during 


HYPERMETROPIA.  109 

the  first  month  or  two  after  the  operation,  or  imtil  the  cicatriza- 
tion has  become  complete,  and  then  it  gradually  diminishes 
for  several  months.  It  usually  does  not  amount  to  more  than 
3  D.,  but  even  a  slight  astigmatism  should  be  sought  out  and 
corrected. 

Even  after  the  most  successful  operations  for  cataract 
vision  very  rarely  equals  |^.  for  the  reason  that  there  is  not 
perfect  transparency  in  the  line  of  vision,  on  account  of  slight 
opacities  on  the  posterior  capsule  of  the  lens,  which  can  often 
be  detected  by  the  ophthalmoscope.  The  amount  of  vision 
varies  very  considerably;  an  acuteness  of  ^%%  (that  is  one-tenth 
of  the  normal  standard)  is  considered  sul^cient  to  class  the 
case  among  the  successful  operations,  while  a  vision  which  will 
enable  the  patient  to  find  his  way  around  is  not  to  be  despised. 

In  adjusting  glasses  for  patients  after  a  cataract  operation, 
it  is  customary  to  wait  until  all  redness  has  disappeared  from 
the  eyes,  which  may  be  a  month  or  two,  and  even  then  they 
should  not  be  worn  constantly  at  first.  In  the  meantime 
smoked  glasses  of  various  degrees  of  tint  axe  worn  as  protec- 
tives.  Tlie  "cataract"  glasses  should  be  set  in  strong  spectacle 
frames,  because  their  great  convexity  makes  them  thick  and 
heavy. 

TWO  PAIRS  OF  GLASSES. 

When  two  pairs  of  glasses  are  required,  for  both  distance 
and  reading,  either  on  account  of  the  high  degree  of  hyper- 
metropia  or  on  account  of  the  approach  of  presbyopia,  there 
are  several  ways  of  arranging  the  glasses  to  meet  the  require- 
ments of  the  person's  occupation. 

In  one  case  two  separate  and  distinct  pairs  of  glasses  may 
be  given,  one  pair  for  distance,  and  the  oth^r  pair  for  reading, 
and  the  patient  changes  from  one  pair  to  the  other,  as  occa- 
sion requires.  This  is  the  best  way  to  place  the  glasses  for 
the  welfare  of  the  eyes  and  is  to  be  recommended  to  patients, 
although  it  involves  so  much  more  trouble  and  the  possibility 
of  not  having  the  second  pair  of  glasses  when  needed,  that 
many  persons  object  to  it  and  prefer  to  arrange  their  glasses 
in  some  other  way. 

In  such  cases  the  person  may  wear  his  distance  glasses 
constantly,  put  them  on  in  the  morning  when  he  arises  and 


110  HYl'ERMETROPIA, 

take  them  oflf  at  night  when  he  retires,  and  then  when  he  wants 
to  read  or  write  or  look  at  small  objects  close  at  hand,  he  places 


an  additional  pair  of  glasses  over  his  distance  glasses,  the  sum 
of  the  two  pairs  being  ec|nal  ifi  strength  to  the  lens  required 
for  reading.  This  extra  pair  of  glasses  may  be  either  in  the 
form  of  eye-glasses,  or  a  spectacle  front  that  should  correspond 
in  dimensions  with  the  frame  that  is  worn  for  distance,  and  in 
place  of  the  usual  temples  is  provided  w^ith  small  hooks  at  each 
end  that  are  readily  fastened  to  the  constant  spectacles,  with 
but  little  danger  of  dropping  or  displacement.  This  is  a  very 
convenient  arrangement,  as  many  hypermetropes  can  testify. 

BI-FOCAL  GLASSES. 

In  other  cases  bi-focal  glasses  are  preferred,  the  upper 
and  larger  portion  being  for  distance,  the  lower  and  smaller 
portion  for  reading.  The  split  bi-focais,  in  which  the  distance 
and  reading  portions  were  of  the  same  size,  are  no  longer 
used,  they  having  given  way  largely  to  the  cemented  form, 
the  reading  strength  being  obtained  by  cementing  a  small  con- 
vex shell  on  the  lower  portion  of  the  distance  glass. 

The  adi-aiiiagcs  of  bi-focal  glasses  to  those  persons  who 
need  assistance  for  both  distance  and  reading,  are  the  conveni- 
ence and  satisfaction  of  having  both  pairs  of  lenses  constantly 
before  the  eyes,  and  only  a  slight  turn  of  the  head  and  eyes 
required  to  bring  either  pair  into  use  as  desired.  Many  per- 
sons wear  this  form  of  bi-focals  with  the  greatest  comfort,  and 
declare  they  could  not  get  along  without  them. 

The  disadc'anfagcs  of  double-focus  glasses  are  the  annoy- 
ance caused  by  the  line  of  separation  between  the  two  glasses 
and  the  dif^culty  in  walking.  This  latter  trouble  is  due  to 
the  fact  that  the  patient  must  look  through  the  reading  glasses, 
and  as  these  are  adapted  for  vision  at  twelve  to  fifteen  inches, 


HYPKRMKTROPIA.  113 

As  this  patient  was  young  and  had  never  worn  glasses,  it 
seemed  advisable  not  to  give  too  strong  a  glass  to  commence 
with,  and  hence  a  pair  of  +  2  D.  were  prescribed  for  constant 
wear.  In  a  week  he  returned  with  the  report  that  his  eyes 
were  free  from  ache  or  pain,  and  that  he  could  read  comfort- 
ably for  two  hours,  which  is  in  marked  contrast  with  the 
moment  or  two's  reading  which  was  his  limit  before. 

It  is  interesting  to  note  that  although  a  mydriatic  was  em- 
ployed, it  was  of  no  real  value  in  determining  the  glasses 
required;  and  the  writer  is  free  to  say  that  he  could  have 
corrected  the  defect  just  as  well  without  the  use  of  the  drug. 
And  w^hat  is  true  in  this  case  applies  equally  to  other  cases,  in 
the  great  majority  of  which  satisfactory  glasses  can  be  pre- 
scribed without  the  thought  of  a  mvdriatic. 


CHAPTER  XII. 


MYOPIA. 


Myopia  is  an  optical  defect,  the  condition  of  its  refraction 
being-  such  that  the  focus  of  parallel  rays  lies  in  front  of  the 
retina.  It  is  the  direct  antithesis  of  hypermetropia,  from 
which  it  diflfers  in  every  respect. 

In  myopia  parallel  rays  of  light  are  converged  to  a  focus 
in  the  vitreous  humor  before  they  have  reached  the  retina. 
After  meeting  in  focus  the  rays  cross  and  continue  until  they 
strike  the  retina  in  circles  of  diffusion ;  consequently,  the  image 
formed  is  blurred  and  indistinct. 


The  Refraction  of  a  Myopic  Eye. 

In  hypermetropia  (as  was  demonstrated  in  the  last  chap- 
ter) the  rays  of  lig^ht  strike  the  retina  before  they  have  had  an 
opportunity  to  unite  in  a  focal  point.  In  myopia,  on  the  other 
hand,  the  rays  have  met  in  focus  and  over-crossed  before  they 
reached  the  retina.  In  both  cases  the  retina  receives  only 
circles  of  diffusion,  and  in  neither  case  is  tlie  formation  of  a 
distinct  image  possible,  this  latter  being  found  only  at  the  prin- 
cipal focus  of  the  eye,  where  the  rays  at  this  point  of  union 
produce  a  sharp  and  well-defined  image. 

FORMS    OF    MYOPIA. 

1.  Refractive  Myopia. 

2.  Axial  Myopia. 

In  the  first  case  there  is  an  excess  in  the  static  refraction 
of  the  eye,  due  to  an  increase  in  the  curvature  of  one  or  more 
of  the  dioptric  surfaces,  or  to  an  augmentation  of  the  index  of 


115 


refraction  of  the  nucleus  of  the  lens,  thus  causing  the  rays  to 
meet  in  focus  too  soon  in  front  of  the  retina,  which  may  be  at 
its  proper  position. 

In  the  second  case,  the  eye-ball  is  too  long-  antcro-pos- 
teriorly  in  the  direction  of  its  visual  axis,  oftentimes  on 
account  of  pathological  changes  in  the  coats  of  the  eye.  This 
removes  the  retina  from  the  principal  focus  of  the  eye,  and  is 
the  form  in  which  myopia  usually  occurs. 

This  elongation  of  the  ball  of  the  eye  depends,  in  the  great 
majority  of  cases,  upon  the  formation  of  a  posterior  staphyloma, 
which  means  a  protrusion  backward.  The  coats  of  the  eye 
first  become  softened  and  thus  are  rendered  liable  to  give  way 
under  pressure;  this  bulging  occurring  at  the  outer  side  of  the 
optic  disk,  toward  the  yellow  spot,  and  causing  a  thinning  of 
the  tissues  and  oftentimes  an  atrophy  of  the  choroid.  This 
elongation  of  the  visual  axis  is  so  constant  that  every  certain 
degree  of  myopia  corresponds  to  a  definite  increase  in  the 
length  of  the  eye-ball. 


AMOUNT  OF  LENGTHENING  OF  VISUAL  LINK  IN  AXIAL  MYOPIA. 

The  following  table  (after  Bonders)  shows  the  increase 
in  length  and  the  total  measurement  that  correspond  to  the 
degree  of  myopia: 


ount  of  Myopia.     Increase  in 

Length.     Length  of  Axis 

.50  D. 

.16  M 

m.                22.98  Mm. 

I 

•32     ' 

23.14      " 

1.50    " 

■49      ' 

23.31       ■■ 

2            " 

.66      • 

23.48      •• 

2.50     " 

.83      • 

2365      " 

3 

1. 01      ' 

23.83      '• 

3-50    " 

1. 19      ' 

24.01       " 

4 

1-37      ' 

24.19      " 

4.50    " 

1-55      ' 

2437      " 

5 

1-74      ' 

24.56      '• 

5.50    '• 

1-93      ' 

24-75      " 

6 

2.13      • 

24.95      " 

6.50  ;; 

2.32      ' 

2514      " 

7 

2.52      ' 

25-34      " 

750  '• 

2.73      ' 

25.55      '• 

8 

2.93      ' 

25-75      " 

8.50    '• 

3-14      • 

25.96      " 

9 

3-35      ' 

26.17      '■ 

950    " 

3.58      ' 

26.40      '• 

10 

3.80      ' 

26.62      •• 

10.50    '■ 

4.0.1      ' 

26.85      •• 

II 

4.26      " 

2708      •• 

116 


MYOPIA. 

Amnunt 

of  Myopia. 

Increase 

in  Length. 

Length  of  .\xiH. 

12 

D. 

473 

Mm. 

27.55  Mm. 

13 

>23 

28.05      " 

14 

5-74 

28.56      " 

IS 

6.28 

29.10      " 

16 

6.83 

29.65      " 

17 

7-41 

30.23      " 

18 

8.03 

30.85      " 

19 

8.65 

31-47      " 

20 

9-31 

32.13      " 

The  antero-jX)steriar  diameter  of  the  normal  eye  is  22.82 
mm.,  which  is  about  iVu.  ^^  ^^  i"ch.  In  the  higher  grades  of 
myopia,  an  increase  of  i  D.  represents  a  much  greater  addition 
in  length  of  the  ball  than  in  the  lower  grades.  For  instance,  a 
myopia  of  i  D.  causes  an  increase  of  -^5^  of  a  millimeter,  as 
compared  with  -jV^the  enlargement  in  an  eye  of  20  D.  myopia 
over  one  of  19  D.,  the  increase  in  the  higher  degree  being  more 
than  twice  as  great  as  in  the  commencement  of  the  defect. 
The  average  increase  for  every  dioptric  of  defect  is  about  ^0^5  of 
a  millimeter,  which  equals  nearly  ^j^  of  an  inch. 

In  an  organ  so  small  as  the  eye,  which  measures  less  than 
an  inch  in  diameter,  the  addition  of  even  Jg-  of  an  inch  cannot 
be  disregarded.  And  when  we  consider  the  eye  as  an  optical 
instrument,  comparable  to  a  photographer's  camera  or  a 
microscope,  and  when  we  call  to  mind  how  the  slightest  move- 
ment of  the  screw  will  throw  both  of  these  instruments  out  of 
focus,  it  can  be  readily  understood  that  the  addition  of  ^jj  of 
an  inch  to  the  length  of  the  eye-ball  is  sufficient  to  disturb  the 
dioptric  adjustment  of  the  eye  and  to  impair  the  clearness  of 
the  image  formed  upon  its  retina. 

In  a  myopia  of  5  D.  the  amount  of  lengthening  is  if 
millimeters,  or  ^^  of  an  inch;  in  a  myopia  of  10  D.  the  amount 
is  3*  millimeters,  or  nearly  ^  of  an  inch;  in  15  D,  of  myopia,  6\ 
millimeters,  or  \  of  an  inch;  while  in  an  extreme  case  of  myopia 
of  20  D.,  9f  millimeters  is  added  to  the  length  of  the  ball, 
which  means  the  addition  of  more  than  -^  of  an  inch,  making 
such  an  eye  measure  i^^  inches  as  compared  with  ||  of  an 
inch,  which  is  the  normal  standard. 

A  careful  study  of  this  table  is  interesting  and  important, 
and  serves  to  impress  upon  the  optician  the  actual  organic 
changes  in  the  coats  and  shape  of  the  eye-ball,  upon  which 
the  production  of  myopia  depends. 


117 


CAUSES   OV   MYOPIA. 

The  one  great  cause  of  myopia  is  loiio^-continued  use  of 
the  eyes  for  small  objects  close  at  liand;  and,  therefore,  myopia 
may  be  considered  as  a  product  of  civilization — as  a  penalty 
of  prog-ressiveness.  The  use  of  the  eye  for  close  vision  calls 
for  an  effort  of  accommodation,  and  when  long  continued, 
may  cause  a  spasm  of  the  ciliary  muscle.  The  adjustment  of 
the  dioptric  apparatus  of  the  eye  for  the  divergent  rays  of  near 
vision,  transforms  it  temporarily  into  a  condition  similar  to 
myopia;  and  if  the  accommodation  continues  its  spasm  and 
fails  to  relax,  a  condition  of  accommodative  myopia  is  produced. 
In  this  case  the  eye-ball  is  not  elongated  and  there  is  no  real 
myopia,  but  all  the  symptoms  are  present  and  the  defect  is 
simulated  by  the  spasm  of  accommodation. 

Tlie  permanent  production  of  real  myopia  depends  upon 
the  congestion,  inflammation  and  giving  way  of  the  coats  of 
the  eye-ball.  Tine  ciliary  muscle  is  connected  with  the  choroid, 
and,  therefore,  in  the  exercise  of  the  function  of  accommoda- 
tion there  is  a  strain  upon  the  latter;  and  when  the  eye  is  over- 
taxed, as  is  frequently  the  case  with  school  children  and  those 
compelled  to  use  their  eyes  continuously  for  near  work,  an 
inflammation  of  the  choroid  is  apt  to  follow. 

In  addition  to  this,  the  close  position  at  which  the  object 
is  held  necessitates  a  marked  convergence  of  the  optic  axes, 
which  causes  a  strain  of  the  muscles  and  a  i)ressure  upon  the 
tunics  of  the  ball.  Then,  too,  the  stooping  position  that  is 
generally  indulged  in  during  such  employment,  also  tends  to 
increase  the  congestion  and  inflammation  by  favoring  an  ac- 
cumulation of  blood  in  the  eye.  In  this  way  a  continuation 
of  the  congestion  and  pressure  gradually  leads  to  a  l)ulging  at 
the  posterior  pole  of  the  eye. 

THE  EFFECT  OF  SCHOOL  LIFE  UPON'  THE  SIGHT. 

There  is  no  doubt  that  the  origin  of  many  distressing 
diseases  can  be  traced  to  the  school  life  of  the  sufferer.  The 
pathological  conditions  are  not  in  all  cases  the  direct  result 
of  unsuitable  school  existence,  but  it  may  be  tiiat  the  im- 
properly   constructed    school    building;^    and    badlx'    managed 


118  MYOPIA. 

school  life  simply  fan  into  a  dame  the  spark  of  heredity  which 
many  unfortunate  children  receive  from  diseased  parents. 

The  deleterious  influence  of  education  and  intellectual 
advancement  upon  the  bodily  health  is  everywhere  apparent. 
Tlie  mind  is  cultivated  at  the  expense  of  the  body,  and  it 
almost  seems  as  if  mental  advancement  goes  hand  in  hand 
with  physical  retrogression.  Certain  it  is,  that  uneducated 
and  untutored  races  present  types  of  bodily  development  supe- 
rior to  those  nations  that  are  renowned  for  civilization  and 
knowledge. 

The  eye  furnishes  a  striking  example  of  the  truth  of  these 
statements.  The  vision  of  those  persons  who  are  engaged  in 
farming  and  kindred  occupations  is  but  seldom  impaired,  while 
in  savage  and  barbarous  races  the  statement  is  made  that 
myopia  and  astigmatism  are  positively  unknown.  We  are  com- 
pelled to  regard  school  life  as  disastrously  prolific  of  refractive 
errors,  by  far  the  most  frequent  of  which  is  myopia. 

SCHOOL  STATISTICS. 

As  early  as  the  beginning  of  the  present  century  the  fact 
was  recognized  that  the  oftentimes  unnatural  requirements  of 
school  life  resulted  in  injury  to  the  eyes  of  many  of  the  chil- 
dren; and  several  writers  in  those  early  days  called  attention 
to  these  important  matters  and  to  the  relation  that  seemed  to 
exist  between  the  demands  of  civilized  life  and  the  production 
of  myopia. 

The  statistics  that  have  been  compiled  bearing  on  this 
subject  are  enormous.  The  examination  of  the  eyes  of  more 
than  ten  thousand  school  children  in  Breslau  and  vicinity  by 
Cohn,  and  the  published  results  of  his  extensive  investigations, 
in  1865  and  1866,  called  public  attention  tO'  school  hygiene  and 
gave  a  great  impetus  to  the  discussion  of  this  important  sub- 
ject. Similar  examinations  have  been  repeated  from  time  to 
time  by  other  observers  in  dififerent  cities,  until  at  the  present 
time  the  children  who  have  been  subjected  to  a  study  of  ocular 
conditions  by  competent  examiners  for  statistical  purposes, 
compose  an  army  of  more  than  two  hundred  thousand.  These 
investigations  have  occurred  in  all  civilized  countries,  and  have 
been  made  under  all  circumstances  of  age,  sex,  race,  health. 


MYOPIA.  119 

heredity  and  schot)!  architecture  and  nianagcnicnt.  Many  of 
these  investigations  have  been  so  arranged  as  to  follow  a  cer- 
tain number  of  pupils  from  class  to  class  and  from  school  to 
school,  and  they  all  point  to  one  inevitable  conclusion,  viz., 
that  mental  culture  is  obtained  at  the  sacrifice  of  ocular  per- 
fection, and  that  such  imperfections  are  usually  myopic  in  their 
nature. 

Certain  facts  have  been  cstal)lislK'(l  by  these  investiga- 
tions, wliich  may  be  brielly  niontioned  as  follows: 

1.  The  eye  at  birth  is  hypermetropic,  and  during  early 
childhood  the  hypermetropic  eyes  greatly  outnumbered  the 
emme'tropic  and  myopic  ones.  An  examination  by  one  ob- 
serv^er  of  children  three  months  old,  showed  them  to  be  all 
hypermetropic. 

2.  Emmetropia  was  comparatively  rare,  but  the  percent- 
age of  those  eyes  which  most  nearly  approached  this  condi- 
tion remained  almost  uniform  throughout  school  life. 

3.  Myopia  was  entirely  absent,  or  very  rare  before  the 
commencement  of  school  life,  and  was  found  to  increase 
steadily  in  percentage  with  the  progress  of  the  pupils  in  the 
schools,  while  the  percentage  of  hypermetropia  diminished 
in  approximately  the  same  degree.  Not  only  does  the  num- 
ber of  myopic  scholars  increase  from  the  lowest  to  the  highest 
schools,  but  the  increase  is  in  direct  proportion  to  the  length 
of  time  devoted  to  the  strain  of  school  life. 

We  cannot  burden  this  chapter  with  the  statistics  com- 
piled by  the  various  European  and  American  observers,  but 
as  Prof.  Cohn's  work  was  the  most  extensive  and  most  not- 
able, and  stands  as  the  representative  of  all  the  others,  we 
give  his  figures  as  follows : 

Primary  schools 1.4  pcr  cent,  of  myopia. 

Elementary  schools 6.7        " 

Intermediate  schools 10.3 

High  schools 19.7 

Gymnasia    26.2 

Universities 59.5 

The  fact  that  in  the  universities  fifty-nine  students  out  of 
every  hundred  are  myopic  is  an  appalling  one,  and  when  con- 
trasted with  the  small  percentage  in  the  primary  schools  (only 


120  MYOPIA. 

one  out  of  every  hundred),  there  is  certainly  abundant  food 
for  the  most  serious  thought,  which  appeals  however  more  to 
those  engaged  in  the  education  of  cliiUlrcn  tlian  to  us  as 
opticians. 

GENESIS   OF   MYOPIA. 

The  manner  in  which  abnormal  circumstances  act  in 
causing  an  elongation  of  the  axis  of  the  eye,  which  is  the 
physical  condition  present  in  myopia,  has  been  well  described 
by  Fenner  in  the  following  graphic  words: 

"As  a  nation  or  community  becomes  wealthy,  refined  and 
elevated  in  social  position,  the  inhabitants  are  more  inclined 
to  cultivate  the  intellectual  faculties;  hence  they  spend  much 
time  in  close  study,  requiring  a  great  and  prolonged  tension 
of  accommodation  in  reading,  writing,  etc.  They  usually  sit 
bending  over  a  desk  in  stooping  position,  the  abdominal 
organs  are  compressed,  preventing  the  free  return  of  the  blood 
from  the  head. 

"The  insufBcient  illumination  at  many  schools  and  col- 
leges necessitates  the  bringing  of  the  eyes  very  near  the  book, 
so  as  to  obtain  a  larger  visual  angle,  and  as  the  book  usually 
rests  on  a  desk  or  table,  the  head  has  to  be  bent  over;  this 
posture  produces  an  increased  flow  of  blood  to  the  eyes,  whilst 
the  higher  degree  of  convergence  necessary  causes  an  in- 
creased pressure  of  the  lateral  recti  muscles  on  the  equator 
of  the  globe,  thus  increasing  the  intra-ocular  pressure. 

"The  congestion  of  the  fundus  oculi  causes  softening  of 
the  scleral  tissue,  which  gives  way  under  the  increased  pres- 
sure, and  the  organ  is  elongated  backward  (a  condition  of 
posterior  staphyloma) ;  the  other  portions  of  the  sclerotic  coat 
are  supported  by  the  broad  muscles.  The  retina  is  then  pushed 
backward  behind  the  focus  of  the  dioptric  apparatus. 

"When  this  condition  once  commences,  all  the  causes 
which  first  gave  rise  to  it,  act  with  increased  force.  There  is 
a  greater  stooping  posture  necessary,  because  the  eyes  have 
to  be  brought  still  nearer  the  object;  an  increased  converg- 
ence is  demanded,  and  the  congestion  of  the  fundus  oculi  in- 
creases; consequently  the  softening  processes  progressively 
augment,   causing   the  posterior  portion   of  the  sclerotic   to 


MYOPIA.  121 

yield  more  and  more.     Hence  myopia  is  usually  progressive, 
particularly  in  its  higher  grades. 

"There  is  greater  tendency  to  the  development  of  this 
condition  of  the  eye  in  youth  from  the  causes  above  men- 
tioned, because  then  the  scleral  tissues  are  softer  and  conse- 
quently more  yielding  than  in  later  life.  With  the  increase  of 
age  this  coat  hardens,  becomes  firmer  and  better  able  to  with- 
stand intraocular  pressure;  hence  it  is  rare  that  the  posterior 
staphyloma  giving  rise  to  near-sightedness  commences  after 
the  twentieth  year." 

V.IIV   CHILDREN   ARE   MORE   PRONE  TO    MYOPIA. 

From  the  foregoing  statements  that  the  development  of 
myopia  depends  upon  a  daily  and  continuous  use  of  the  eyes 
upon  small  objects  close  at  hand,  accompanied  by  strong 
convergence  and  with  the  patient  in  a  stooping  posture,  it 
might  naturally  be  expected  to  find  this  error  of  refraction  of 
frequent  occurrence  among  tailors,  seamstresses,  embroidery 
and  lace  makers,  and  all  artisans  whose  trades  require  accurate 
near-vision. 

But  the  fact  is  myopia  is  much  more  rare  among  these 
people  than  in  the  wealthier  and  more  intellectual  classes. 
This  apparent  paradox  can  be  explained  as  follows:  these 
working  people  do  not  engage  in  their  occupations  until  they 
are  of  adult  size,  when  the  tissues  of  the  sclerotic  and  the  other 
coats  of  the  eye  have  become  suflficiently  firm  to  resist  the 
disturbing  influences  which  their  work  engenders.  While  in 
the  case  of  the  higher  classes,  the  eyes  are  exposed  to  the  dan- 
gers of  myopia  at  the  tender  age  at  which  these  children  are 
usually  placed  at  school. 

In  addition  to  the  difference  in  the  ages  of  these  two 
sets  of  people,  there  is  probably  another  factor  that  is  brought 
into  action,  and  that  is  the  well-known  fact  that  when  the 
mind  is  actively  engaged  in  study,  an  increased  quantity  of 
blood  flows  through  the  brain,  causing  a  temporary  conges- 
tion, which  is  shared  by  the  eye  on  account  of  its  proximity, 
thus  adding  to  the  previous  plethora  of  the  fundus  of  this 
organ. 


122 


ANATOMICAL  CHANCES  IN  THE  FUNDUS  OF  THE  MYOPIC  EYE. 

In  view  of  what  has  been  said,  that  myopia  means  staphy- 
loma and  that  the  degree  of  myopia  corresponds  to  the 
amount  of  extension  of  the  fundus,  it  follows  that  myopia 
and  posterior  staphyloma  are  almost  synonymous  terms,  and 
it  is  evident  that  the  myopic  eye  is  essentially  a  diseased  eye, 
more  so  than  any  other  error  of  refraction.  The  invention 
of  the  ophthalmoscope  places  in  our  hands  the  means  of 
observing  the  changes  taking  place  in  the  fundus  of  the  eye 
upon  which  the  production  of  myopia  depends,  and  of  noting 
the  progress  of  the  morbid  processes. 

The  extension  of  the  globe  of  the  eye  is  at  the  expense 
of  the  sclerotic  coat,  which  grows  thinner  and  thinner,  until  in 
high  degrees  of  myopia  it  becomes  transparent,  and  some- 
times when  the  eye  is  turned  inward,  the  dark  pigment  of  the 
choroid  becomes  visible  through  it.  As  the  property  of  the 
dense  and  firm  sclerotic  coat  is  to  give  the  eye  its  form  and 
to  support  its  interior  structure,  it  naturally  follows  if  this  pro- 
tecting coat  be  stretched  at  any  part,  the  contents  of  the  eye- 
ball lying  adjacent  to  this  will  suffer  a  corresponding  change 
in  position. 

Thus  it  happens  that  the  choroid  coat  also  becomes  ex- 
tended and  atrophied,  particularly  on  the  outside  of  the  optic 
disk,  as  well  as  in  the  region  of  the  yellow  spot. 

THE   MY'OPIC   CRESCENT. 

The  choroid  attains  its  greatest  thinness  around  the  outer 
edge  of  the  optic  disk,  where  it  forms  a  white,  shining  con- 
centric disk,  resembling  a  meniscus  in  shape.  The  dark  pig- 
ment cells  are  obliterated,  the  small  capillary  blood-vessels  no 
longer  carry  the  red  blood,  and  there  remains  the  marble- 
white,  crescent-shaped  patch  of  atrophy.  If  the  distension 
extends  entirely  around  the  disk,  the  atrophic  portion  becomes 
annular  in  shape. 

The  ophthalmoscope  admits  of  careful  observation  of 
these  changes.  Some  remains  of  pigment  are  often  seen  about 
the  convex  border  of  the  crescent.  Although  the  atrophy 
usually  assumes  the  crescentric  form,  vet  it  mav  varv,  some- 


MYOPIA.  123 

times  forming  a  complete  ring  around  the  disc  as  already 
stated,  or  extending  outward  in  an  irregular  patch.  This  in- 
crease in  atrophic  surface  around  the  optic  nerve  enlarges 
the  size  of  the  normal  blind  spot. 

The  presence  of  the  crescent  just  described  depends 
largely  upon  the  degree  of  myopia;  in  slight  cases  in  young 
persons  it  may  be  entirely  absent,  but  in  cases  of  6  D.  and 
over  in  adult  persons  it  is  almost  invariably  present. 

The  position  of  the  yellow  spot  may  also  be  changed;  it 
approaches  the  posterior  pole  of  the  eye-ball  until  the  visual 
line  almost  corresponds  with  the  optic  axis.  In  very  high 
degrees  of  the  defect,  it  may  even  pass  to  the  inside  of  the  axis 
of  the  ball. 

HEREDITY. 

JNIyopia  is  regarded  as  an  hereditary  disease,  and  there 
is  a  universal  popular  impression  that  the  defect  is  handed 
down  from  parent  to  child.  When  a  myopic  patient  is  ques- 
tioned, he  can  usually  name  some  other  member  of  his  family 
as  being  similarly  affected,  perhaps  a  parent  or  grandparent, 
an  uncle  or  aunt,  a  brother  or  sister. 

But  there  are  many  difficulties  that  stand  in  the  way  of  a 
thorough  investigation  of  hereditary  influence,  and  perhaps 
all  that  can  be  claimed  is  that  a  predisposition  to  myopia  is  often 
transmitted  to  posterity,  and  not  the  disease  itself.  So  that 
it  may  be  regarded  as  an  established  fact  that  myopia  rarely 
develops  in  an  emmetropic  eye,  and  never  in  a  hypermetropic 
eye,  Avithout  a  predisposition  to  it  derived  from  ancestors. 

rREVENTIVE   MEASURES. 

Whatever  an  ounce  of  prevention  may  be  to  other  mem- 
bers of  the  body,  it  certainly  is  worth  many  pounds  of  cure  to 
the  eye.  This  delicate  organ  will  stand  a  great  deal  of  use, 
and  not  a  little  abuse,  but  when  once  thrown  off  its  balance, 
it  very  rarely  can  be  brought  back  to  its  original  perfection  of 
action,  and  it  becomes  liable  ever  after  to  a  return  of  disability 
of  function. 

On  this  account  and  from  the  fact  that  modern  civiliza- 
tion has  imposed  upon  the  eye  an  ever-increasing  amount  of 
strain,  one  might  suppose  that  the  greatest  precaution  would 


124  MYOPIA. 

be  observed  to  maintain  the  or^^an  in  a  condition  of  healtli. 
And  yet  it  is  safe  to  say  that  there  is  no  organ  in  the  body, 
the  welfare  of  which  is  so  persistently  neglected  as  the  eye. 

It  is  not  uncommon,  and  certainly  not  improper,  to  have 
the  first  teeth  of  children  four  and  live  years  of  age  filled  in- 
stead of  extracted;  while  the  eye,  the  most  intellectual,  the 
most  apprehensive,  and  the  most  discriminating  of  all  our 
organs,  receives  scarcely  a  passing  thought,  much  less  an  ex- 
amination. 

now   THE   CHILD   SUFFERS. 

It  seems  never  to  occur  to  parents  that  the  principal 
agent  in  acquiring  an  education  is  the  eye.  The  child  is 
placed  in  school  without  the  slightest  inquiry  on  the  part  of 
either  parent  or  teacher  as  to  whether  it  has  the  normal 
amount  of  sight,  w^hether  it  be  near-sighted  or  far-sighted, 
whether  vision  is  clear  or  blurred,  whether  it  sees  with  one  eye 
or  two  eyes,  or  whether  the  act  of  vision  is  accomplished  at 
the  expense  of  an  unnatural  strain  upon  the  nervous  system. 

It  has  been  trutlifully  said,  and  cannot  be  repeated  too 
often,  that  "a  near-sighted  eye  is  a  sick  eye,"  and  it  not  infre- 
quently happens  that  a  near-sighted  child  is  a  sick  child,  the 
reason  for  which  is  as  follows:  a  myopic  boy  is  unable  to 
successfully  compete  with  his  schoolmates  in  their  usual 
games,  for  the  reason  that  most  of  them  lie  beyond  the  range 
of  his  vision.  Subjected  to  ridicule  on  the  part  of  his  com- 
panions for  clumsiness  and  inaptitude,  due  to  a  defect  of  which 
neither  he  nor  they  are  aware,  he  relinquishes  in  disgust  one 
by  one  of  the  health-giving  sports  in  which  he  can  never  hope 
to  excel,  and  takes  to  books  until  reading  becomes  a  passion. 

Not  only  the  abstraction  from  fresh  air  and  exercise,  but 
the  ver}-  conditions  under  which  the  eyes  are  used,  are  detri- 
mental to  the  general  health.  The  book  is  brought  nearer  the 
eye,  the  head  is  bent  upon  the  chest  or  over  the  table,  till  the 
shoulders  become  curved  and  the  chest  contracted,  and  normal 
respiration  is  interfered  with. 

Such  a  child  cannot  see  clearly  the  features  of  his  com- 
panions, his  parents  or  his  teachers,  nor  catch  the  ever-varying 
expression  of  the  eye,  or  the  subtle  change  in  the  muscles  of 
the  face,  by  which  an  idea  is  emphasized  or  a  principle  en- 


MYOPIA.  125 

forced.  His  sense  of  the  beautiful  in  nature  is  hampered  and 
curtailed.  Earth,  sea  and  sky  make  up  for  him  a  world  dif- 
ferent from  that  of  his  companions,  and  it  is  no  wonder  that 
his  views  of  men  and  things  are  different  also. 

He  judges  of  men  and  their  intentions  rather  by  the  sound 
of  the  voice  than  the  expression  of  the  face,  and  is  apt  for  that 
reason  to  be  suspicious  of  strangers.  In  unfamiliar  neighbor- 
hoods and  with  insufficient  light,  he  is  timid  and  cautious. 
With  all  this  studiousness  and  devotion  to  books,  the  state- 
ment is  made  that  near-sighted  people,  as  a  whole,  are  not  any 
more  intellectual  than  those  who  have  normal  eyes,  because 
studiousness  and  intellectuality  are  not  always  convertible 
terms,  as  most  people  think  they  are. 

Of  course  these  remarks  do  not  apply  to  those  cases  of 
myopia  which  have  been  corrected  at  the  commencement  of 
school  life  with  the  proper  concave  lenses,  but  to  those  other 
cases  of  the  defect  which  exist  among  young  and  growing 
children  and  which,  bejng  neglected,  gradually  become  worse 
as  adult  age  is  reached, 

ORIGIN  OF  THE  TERM  MYOPIA. 

In  hypermetropia,  as  was  demonstrated  in  the  last  chapter, 
the  patient  is  able,  by  the  use  of  the  accommodation,  to  over- 
come the  defect  and  maintain  clear  vision.  But  in  myopia,  on 
the  contrary,  the  exercise  of  the  accommodation  would  only 
make  the  eye  more  near-sighted;  nor  does  the  eye  possess 
any  other  power  of  its  own  to  correct  this  error  of  refraction, 
except  that  such  a  patient  falls  into  the  habit  of  half-closing 
the  lids,  or  nipping  them  together.  In  this  way  the  more  cir- 
cumferential rays  are  cut  of¥  and  the  central  rays  only  are 
allowed  to  enter  the  eye,  the  lids  thus  forming  a  stenopaic 
apparatus  to  the  improvement  of  the  clearness  of  the  image 
formed  on  the  retina.  This  gives  rise  to  the  word  myopia, 
which  is  derived  from  two  Greek  words,  meaning  to  "contract 
or  close  the  eve." 


126 


Diagram  of  a   Myopic   Eye,    showing  fhat  the   divergent   rays 
wliicli  proceed  from  F.  P.  (the  far  point)  are  exactly 


focused  upon  the  retina 
HOW    DIVERGENT    RAYS   ARE    FOCUSED     IN    MYOPIA. 

When  parallel  rays  pass  through  a  convex  lens,  they  are 
brought  to  a  focus  at  a  certain  point  on  the  other  side  of  the 
lens,  which  is  known  as  the  principal  focus  of  the  lens.  If 
divergent  rays  are  made  to  pass  through  the  same  lens,  the 
focus  would  be  farther  away;  while  in  the  case  of  convergent 
rays  the  focus  would  be  nearer  than  the  principal  focus. 

The  statement  has  been  made  in  this  chapter  that  in 
myopia  the  rays  meet  in  front  of  the  retina,  but  it  should  be 
remembered  that  this  refers  only  to  parallel  rays,  or  to  con- 
vergent rays  which  focus  still  farther  in  front.  The  focus  of 
divergent  rays  is  farther  back  than  parallel,  thus  approaching 
the  retina,  and  if  of  the  proper  degree  of  divergence  will  meet 
on  this  membrane. 

Now  in  nature  there  are  no  convergent  rays  of  light ;  such 
rays  exist  only  when  made  so  artificially.  Hence  we  are  inter- 
ested at  the  present  time  only  in  parallel  and  divergent  rays, 
the  two  forms  in  which  we  find  light  to  exist,  the  former  pro- 
ceeding from  distant  objects  and  meeting  in  front  of  the  retina 
of  the  myopic  eye;  the  latter  issuing  from  objects  near  at  hand 
and  focussing  on  the  retina  as  shown  by  the  diagram. 

There  is  in  front  of  the  myopic  eye  a  certain  space  within 
which  vision  is  clear  and  beyond  which  it  becomes  indistinct, 
the  dividing  line  of  which  is  marked  by  the  far  point,  which 
varies  with  the  degree  of  defect.  The  higher  the  grade  of 
myopia  the  closer  the  far  point,  the  lower  the  degree  the  more 
distant  the  far  point.  It  follows  from  this  that  if  any  object 
can  be  brought  close  enough  to  be  within  the  far  point  of  any 


MYOPIA.  127 

myopic  eye,  it  will  be  clearly  seen.  While  if  it  is  moved  farther 
away  so  as  to  get  beyond  the  far  point,  the  rays  begin  to  lose 
their  divergence  and  focus  in  front  of  the  retina  and  vision  is 
no  longer  distinct.  Thus  it  is  seen  that  the  myope  is  shut  up 
in  a  little  world  of  his  own,  the  limits  of  which  are  determined 
by  the  distance  of  the  far  point. 

In  the  correction  of  myopia,  the  concave  lens  that  is  pre- 
scribed causes  the  rays  that  pass  through  it  to  enter  the  eye 
divergently,  thus  throwing  the  focus  back  upon  the  retina,  and 
restoring  distant  vision  to  normal  clearness. 

PREVALENCE  OF  MYOPIA  AND  ITS  COMPARATIVE  FREQUENCY  IN 
DIFFERENT   CLASSES   OF   SOCIETY. 

^lyopia  is  more  common  in  the  cities,  and  in  those  nations 
and  among  those  classes  of  people,  whose  advanced  civiliza- 
tion, and  w^hose  occupations  require  extended  use  of  the  eyes 
for  close  objects.  It  is  not  equally  prevalent  in  all  civilized 
countries,  nor  in  all  parts  of  the  same  country. 

It  is  much  less  frequently  found  among  persons  brought 
up  in  rural  districts,  or  among  those  who  devote  themselves 
to  occupations  requiring  but  little  use  of  sharp  vision  for  small 
objects.  On  the  contrary  it  is  among  this  class  that  hyper- 
metropia  prevails  to  a  much  greater  extent. 

VISION    OF   MYOPES. 

It  is  not  unusual  to  find  in  the  slighter  degrees  of  myopia, 
where  the  error  of  refraction  is  less  than  2  D.,  that  the  patient 
himself  is  not  conscious  of  its  existence,  until  perhaps  it  is 
accidentally  discovered  when  comparing  distant  vision  with 
some  emmetropic  friend;  or  by  tr>ing  on  the  concave  glasses 
of  some  myopic  friend,  when  it  is  found  that  everything  is 
more  clearly  seen  and  objects  arc  visible  at  greater  distances. 

With  such  a  myopia  the  patient  will  be  able  to  read  fine 
print  without  convex  glasses  until  he  is  probably  fifty  or  fifty- 
five  years  of  age.  Thus  the  late  appearance  of  presbyopia 
will  tend  to  compensate  for  the  diminished  range  of  vision  for 
distant  objects.  It  is  for  these  reasons  that  Donders  gives 
his  preference  to  the  slightly  myopic  eye,  because  he  argued 


128  MYOPIA. 

that  the  slight  iiuhstinctness  with  which  distant  objects  are 
seen  in  early  life,  is  more  than  counterbalanced  by  the  ability 
to  read  and  write  at  a  later  period  of  life  without  the  use  of 
convex  glasses. 

In  higher  degrees  of  myopia  if  there  is  a  fair  amplitude  of 
acconunodation  present,  the  patient  naturally  falls  into  the 
habit  of  bringing  small  objects  close  to  the  eyes,  oftentimes 
much  nearer  than  there  is  any  necessity  for,  and  as  it  is  in- 
convenient to  bring  his  book  or  work  close  to  his  eyes,  he 
bends  the  body  so  as  to  assume  a  stooping  position,  the  more 
so  the  higher  the  degree  of  defect. 

The  half-closed  lids  and  the  wrinkling  of  the  skin  of  the 
forehead,  gives  the  features  a  peculiar  expression,  by  which 
the  myope  can  often  be  recognized;  and  this  habit,  like  many 
others  when  once  formed,  is  hard  to  abandon  and  is  often  kept 
up  even  after  the  myopia  has  been  entirely  corrected  by  con- 
cave glasses,  and  the  necessity  for  using  the  lids  as  a  stenopaic 
apparatus  no  longer  exists. 

As  has  already  been  stated,  objects  situated  beyond  the 
far  point  are  seen  in  diffusion  circles;  while  within  this  point 
vision  is  just  as  good  as  in  an  emmetropic  eye,  or  perhaps  even 
a  little  better.  Inasmuch  as  small  objects  in  order  to  be  sharply 
defined,  must  necessarily  be  held  much  closer  in  this  defect 
than  normal,  the  visual  angle  under  which  they  are  seen  is 
proportionally  larger;  consequently  the  image  formed  on  the 
retina  is  of  greater  size,  thus  impressing  more  of  the  percipient 
elements  of  the  layer  of  rods  and  cones. 

In  addition  to  this  the  pupil  is  more  dilated  in  myopia, 
thus  allowing  additional  light  to  enter  the  eye  and  enabling 
the  patient  to  see  with  less  illumination.  But  while  near  vision 
is  possible  with  a  feeble  light,  distant  vision  on  the  contrary 
is  improved  by  a  brilliant  illumination,  because  the  strong 
light  contracts  the  pupil  and  thus  diminishes  the  size  of  the 
diffusion  circles.  For  this  reason  the  myope  can  see  very 
much  better  by  looking  through  the  pin-hole  disk  from  the 
trial  case. 

When  the  degree  of  myopia  is  greater  than  6  D.,  there  is 
generally  more  or  less  disturbance  of  near  vision  in  addition 
to  the  impairment  of  distant  vision,  and  this  is  not  to  be  won- 


y\\o\'\.\.  129 

dered  at  wlion  the  morbid  clian,L;cs  that  have  taken  place  at  the 
fundus  of  the  eye  are  euusidered.  I'.xcessive  use  of  the  eyes 
in  near  vision  i)roduces  a  fecHnj^-  of  strain  and  they  become 
])ainful :  follo\vini>-  which  there  apjiears  redness  of  the  con- 
junctiva and  an  increased  llow  of  tears. 

Misc.M  \()i.ri  A.\ii:s. 

in  all  form  of  ametropia,  but  especiall\  in  myopia,  C(jui- 
plaints  are  often  made  of  dark  sjjots  or  lloating  bodies, 
whicli  make  their  a])pearance  in  the  field  of  vision  and  dance 
before  the  e\es,  and  which  have  received  the  name  of  mnsccc 
ivlitaiitcs.  The  constant  appearance  of  these  floating  sjjecks 
is  a  source  of  considerable  aiuioyance  and  alarm  to  myopes, 
not  only  from  the  way  in  which  they  eng-age  the  attention,  but 
also  from  the  fears  which  they  excite. 

They  are  variously  described  by  different  persons,  and  are 
most  noticeable  when  the  eyes  are  turned  toward  a  white  sur- 
face, such  as  a  white-washed  wall  or  ceiling,  or  a  white  cloud. 
Tlie\-  follow  the  movements  of  the  eye,  and  are  especially 
annoying  dm-ing  the  act  of  reading  as  they  float  across  the 
])age.  Thev  do  not,  however,  interfere  with  vision,  as  it  is 
characteristic  of  them  that  they  never  cross  the  axis  of  vision, 
nor  obscure  or  conceal  the  object  looked  at.  but  rather  move 
about  the  lateral  jiortions  of  the  field. 

There  is  no  real  opacity  of  the  vitreous  humor,  and  an 
examination  by  the  ophthalmoscope  fails  to  detect  in  these 
cases  any  floating  opa(|ue  particles.  They  are  caused  by 
shadows  thrown  upon  the  retina  by  very  minute  particles  in 
the  vitreous  body,  perhaps  the  remains  of  embryonic  tissues. 
They  are  more  visible  to  myopic  persons  than  to  others,  be- 
cause of  the  greater  length  of  the  eye-ball,  thus  allowing  a 
shadow  of  larger  size  to  he  cast  upon  the  retina.  The  nund)er 
of  these  spots  may  be  increased  by  any  condition  which  dis- 
turbs the  balance  of  the  circulation  and  thus  alters  the  density 
of  the  fluids  within  the  eye. 

If  not  excessive  in  size  or  nund)er.  these  spots  may  l)e 
regarded  as  more  or  less  physiological  and  the  effort  must 
be  made  by  the  individual  to  ignore  them.  I'atients  often 
complain  of  the  exaggerated  and  fantastic  shai)es  they  assume. 


130  MYOPIA. 

ascrihiiij;-  tlioni  to  disorders  of  digestion  and  torpidity  of  the 
liver.  r>ut  when  they  are  al)uiulant  and  increasing-,  they  may 
indicate  serious  structural  chang-e,  and  should  lead  to  a  careful 
examination  by  a  competent  oculist. 

Donders  says:  "I  have  seen  instances  in  which  anxietv 
about  muscce  vt)litantes  aniountetl  to  true  monomania,  against 
which  all  reasoning  and  the  most  direct  demonstrations  were 
in  vain." 

Any  marked  increase  in  the  size  and  number  of  these  spots 
may  be  regarded  as  evidence  of  morbid  changes  taking  place 
in  the  vitreous  humor,  and  if  they  become  so  bad  as  to  seri- 
ously disturb  vision,  an  examination  by  the  ophthalmoscope 
will  generally  reveal  turbidity  in  this  humor.  Sometimes 
there  arc  such  subjective  symptoms  as  sparks,  luminous  chains, 
flashes  of  lig^ht,  brightly  illuminated  white  or  colored  rings, 
which  often  appear  in  the  field  of  vision :  they  are  more  notice- 
able in  darkness  than  in  daylight  and  are,  of  course,  very 
alarming  to  the  sufferer.  Their  appearance  is  an  indication 
that  some  serious  condition  is  impending  in  the  fundus  of  the 
eye,  and  which  may  result  in  amblyopia.  Even  after  the  onset 
of  these  unpleasant  symptoms,  if  great  care  is  exercised  in 
the  use  of  the  eyes  and  all  excesses  and  irregularities  of  habits 
are  avoided,  vision  may  be  preser\'ed  in  a  fairly  good  condition 
for  a  long  time. 

The  myopic  eye  is  more  liable  to  be  attacked  by  disease  of 
its  internal  structures  than  is  the  emmetropic  eye:  as  choroi- 
ditis, which  often  leads  on  tO'  hyalitis  and  inflammation  of  the 
vitreous,  conditions  which  are  serioiis  and  very  much  to  be 
dreaded:  hence  the  great  importance  of  care  in  the  use  of  such 
eyes,  which  require  careful  watching  in  order  that  complica- 
tions may  be  early  detected  and  receive  skillful  treatment. 

DETERMINATION  OF  THE   ENISTENCE  OF  MYOPIA. 

The  presence  of  myopia  and  its  degree  can  be  readily  de- 
termined by  the  test  letters  of  Snellen,  which  are  hanging  on 
the  wall  twenty  feet  away. 

If  the  patient  is  able  to  read  the  No.  20  line  there  can  be 
no  myopia;  if,  however,  he  cannot  see  the  letters  on  this  line, 
but  can  perhaps  barely  distinguish  some  of  the  larger  lines,  a 


MYOPIA.  131 

weak  convex  lens  is  placed  before  the  eyes;  this  at  once  blurs 
the  vision  and  excludes  hypernietropia.  A  convex  lens  is  used 
as  a  matter  of  proper  routine,  even  though  the  symptoms  all 
indicate  myopia,  in  order  to  escape  the  grievous  error  of  mis- 
taking hypcrmetropia  for  myopia,  as  has  been  frequently  done, 
to  the  discredit  of  the  optician  and  the  suffering  of  the  patient. 

After  this  procedure  the  way  is  clear  tor  the  use  of  con- 
cave lenses;  a  weak  one  is  first  tried  which  instantly  clears 
vision  and  enables  more  letters  to  be  seen.  A  stronger  one  is 
used  with  the  result  of  a  still  greater  improvement;  thus  by 
a  gradual  increase  in  the  power  of  the  lenses  the  acuteness  of 
vision  is  brought  up  to  |g  clearly  and  sharply.  This  proves 
the  existence  of  myopia,  and  the  number  of  glasses  will  indi- 
cate the  degree  of  the  defect. 

As  soon  as  the  vision  is  raised  to  fg,  the  optician  must 
stop,  because  then  he  has  measured  the  grade  of  the  myopia. 
In  this  defect  it  is  a  not  uncommon  thing  for  glasses  to  be 
prescribed  very  much  stronger  than  are  really  necessary.  If 
the  patient  is  not  old,  and  the  power  of  accommodation  unim- 
paired, an  increase  in  the  strength  of  the  glasses  will  allow  the 
distant  type  to  be  seen  equally  well  or,  perhaps,  even  a  little 
better. 

When  a  concave  lens  is  placed  before  a  myopic  eye  of 
greater  strength  than  is  necessary  to  neutralize  the  defect,  the 
eye  is  rendered  hypermetropic  and  the  ciliary  muscle  is  called 
into  action  to  overcome  the  diminishing  effect  of  the  minus 
lens,  just  as  is  the  case  in  hypernietropia.  This  tension  of  the 
accommodation  carries  with  it  a  contraction  of  the  pupil 
(which  in  myopia  is  apt  to  be  large),  thus  cutting  of  the 
peripheral  rays  and  acting  on  the  principle  of  the  pin-hole  disk, 
improves  the  distant  vision.  Hence  there  is  a  constant  tend- 
ency for  the  glasses  chosen  in  myopia  to  be  stronger  than  are 
necessary,  and  such  glasses  at  once  begin  to  strain  and  irritate 
the  eye. 

This  logically  leads  to  the  rule  that  is  laid  down  in  myopia. 
that  tJw  very  zvcakcst  glasses  with  which  the  No.  20  line  can  be 
seen  at  twenty  feet,  are  the  proper  ones  to  prescribe.  In 
hypcrmetropia,  it  will  be  remembered,  the  strongest  convex 
glasses   which   were   accepted   at   twenty   feet,    were    recom- 


132  MYoriA. 

mended;  in  myopia,  the  weakest  concave  glasses.  The  reason 
is  the  same  in  both  cases:  to  assist  the  accommodation  or  at 
least  to  avoid  overtaxing  ii.  Tlie  stronger  the  convex  glasses 
the  more  support  given  to  ilic  ciliary  muscle;  the  weaker  the 
concave  glasses  the  less  tax  upon  this  muscle. 


Dl.Vf.NOSIS  OF  MYOPIA. 

The  diagnosis  of  myopia  is  not  usual!}-  a  difficult  matter. 
Distant  vision  is  below  the  standard,  and  is  at  once  raised  to 
normal  by  the  proper  concave  lenses.  The  impairment  of  dis- 
tant vision  by  itself  is  not  an  evidence  of  myopia,  because  this 
may  be  present  in  a  great  many  other  conditions.  But  when 
this  diminished  acuteness  of  vision  instantly  yields  to  the 
proper  concave  lenses,  the  proof  is  positive  that  the  case  is 
one  of  myopia  and  nothing  else.  In  cases  of  impaired  vision 
from  other  causes,  the  application  of  concave  lenses  will  pro- 
duce little  if  any  improvement. 

In  the  chapter  on  hypermetropia  great  stress  was  laid  on 
the  importance  of  distinguishing  that  defect  from  myopia,  and 
the  reader  was  warned  that  impaired  distant  vision  and  hold- 
ing objects  close  to  the  eyes,  did  not  necessarily  indicate 
myopia,  but  might  occur  in  hypermetropia.  The  skilled  and 
wide-awake  optician  will  hardly  fall  into  this  error,  and  yet  it 
has  happened  quite  often  among  mere  spectacle  sellers,  and 
thus  tends  to  bring  discredit  upon  opticians  as  a  class. 

In  any  case  of  impaired  vision  where  it  is  desired  to 
measure  the  refraction  by  trial  lenses,  the  invariable  rule  is  to 
commence  the  test  zcith  convex  lenses,  and  if  they  are  accepted  at 
all,  the  case  is  regarded  as  one  of  hypermetropia  and  concave 
lenses  must  not  be  tried.  Perchance  the  latter  were  placed 
before  the  eye,  they  w'ould  most  likely  be  accepted  also;  then 
the  case  would  be  obscured  and  the  optician  in  a  quandary — 
convex  and  concave  lenses  both  accepted,  which  is  correct? 
But  if  the  rule  just  mentioned  be  adhered  to,  the  case  is 
kept  free  from  any  such  doubt.  Then,  if  convex  lenses  are 
absolutely  rejected,  it  is  proper  to  try  concaves,  and  if  the 
latter  raise  the  vision  to  normal,  myopia  must  be  the  defect 
that  is  present. 


133 


MYOPIA  AND  AMIiLVOPIA. 


The  term  amblyopia  usually  sig-nifies  (Uiihiicss  of  vision, 
and  as  this  is  the  one  prominent  symptom  of  myopia,  there  is 
some  danger  that  the  two  conditions  may  be  confounded.  In 
both  cases  the  acuteness  of  vision  is  impaired,  and  there  is  the 
tendency  to  bring  small  objects  very  close  to  the  eyes  in  order 
to  get  the  benefit  of  the  magnified  retinal  images. 

Strictly  speaking,  amblyopia  i's  only  a  symptom;  it  is  a 
term  used  to  express  the  defective  vision  from  which  the  patient 
suflfers,  which  is  not  dependent  upon  an  error  of  refraction,  but 
is  due  to  functional  disturbance  or  disease  of  some  part  of  the 
visual  apparatus,  either  the  retina,  the  optic  nerve  or  the  brain. 
It  is  possible  that  this  condition  may  exist  without  any  evi- 
dences of  it  visible  to  the  ophthalmoscope,  although  wc  usually 
expect  to  find  some  atrophy  of  the  optic  nerve. 

Tliis  is  not  the  place  to  give  a  detailed  description  of 
amblyopia,  but  wc  will  simply  mention  some  of  the  forms  in 
which  it  occurs:  congenital  or  acquired,  temporary  or  per- 
manent, and  symmetrical  or  non-symmetrical,  .linblvopia  ex 
anopsia  is  due  to  lack  of  use  of  eyes;  reflex  amblyopia  to  irrita- 
tions in  some  other  part  of  the  body;  traumatic  amblyopia  to 
injury;  urcrmic  amblyopia  to  kidney  disease;  tobacco  and  alcoJwl 
amblyopia  to  abuse  of  these  agents;  Jiysferical  amblyopia,  Jiiglit- 
biindiicss,  day-blinditess.  etc. 

The  one  diagnostic  feature  of  amblyopia  b\-  which  the 
optician  will  be  able  to  recognize  it.  is  its  inability  to  respond 
to  any  glass  that  may  be  placed  before  it,  and  the  failure  of 
the  pin-hole  disk  to  afTord  the  slightest  improvement  in  the 
acuteness  of  vision.  By  attention  to  these  points  myopia  can 
always  be  readily  distinguished  from  amblyopia. 

Ni:.\R  x'lsiox  IS  (tOon. 

While  in  myopia  the  distaiU  vision  is  very  nnich  impaired, 
at  the  same  time  the  near  vision  is  quite  goo<l,  and  the  recog- 
nition of  myopia  is  made  possible  by  the  existence  of  these  two 
factors.  If  either  one  of  them  is  missing  it  cannot  be  myopia; 
while  if  both  are  present  there  is  little  room  for  doubt. 


134  MYOPIA. 

'IMicrc  are  ven-  good  reasons  why  close  vision  should  be 
good  in  myopia.  Such  an  eye  by  its  refractive  condition  is 
adapted  for  near  vision,  the  divergent  rays  of  which  are 
focused  without  any  acommodative  effort,  and  hence  read- 
ing, writing  and  sewing  may  be  done  without  any  tax  on  the 
ciliary  muscle.  Then,  too,  on  account  of  the  excess  of  re- 
fractive power  which  such  an  eye  possesses,  there  is  a  slight 
magnification  of  the  image  formed  on  the  retina,  and  hence 
small  print  and  fine  stitches  in  sewing  which  might  be  intol- 
erable to  other  eyes,  are  quite  possible  to  the  myope. 

On  account  of  this  sharpness  of  proximate  vision,  near- 
sighted persons  consider  themselves  fitted  for  occupations  re- 
quiring good  vision  for  small  objects  close  at  hand,  as 
engraving,  watch-making,  etc.,  but  if  the  occasion  presents 
itself  they  should  be  warned  that  myopic  eyes  are  usually  sick 
eyes,  and  if  their  defect  is  of  high  degree  they  should  be  ad- 
vised against  the  choice  of  these  trs-ing  occupations,  and 
recommended  to  others  that  do  not  require  such  contiguous 
use  of  the  eyes. 

How  often  do  we  see  persons  bending  over  their  desks 
when  writing,  with  their  eyes  very  close  to  the  paper  or  some- 
times looking  obliquely  at  it.  This,  in  many  cases,  is  only  a 
habit,  and  ma}'  occur  with  emmetropes  or  with  those  only 
slightly  myopic;  but  habits  once  former  are  hard  to  break,  and 
gradually  such  changes  take  place  in  the  eye  that  develop  or 
increase  the  myopia,  and  the  near-sight  that  was  once  a  habit 
becomes  a  necessity. 

If,  at  the  commencement  of  these  symptoms,  the  patient 
is  advised  of  their  serious  tendency,  and  is  instructed  how  to 
avoid  the  danger,  by  keeping  the  book  at  the  proper  distance, 
by  holding  the  head  erect  and  by  frequently  resting  the  eyes 
in  looking  for  a  few  minutes  at  distant  objects,  the  trouble  can 
probably  be  nipped  in  the  bud  and  the  eye  prevented  from 
becoming  myopic. 

so    MANY    PERSONS    WEARING    GLASSES. 

The  middle-aged  individual  of  to-day  is  astonished  as  he 
walks  along  the  streets  at  the  great  number  of  persons  wearing 
glasses,  and  he  is  particularly  struck  by  the  large  proportion 


MYOPIA.  135 

of  sp<?ctaclcil  cliildren.  \\c  hears  so  many  vdun.cc  people  eoni- 
plaining  of  their  eyes,  that  he  invohmtarily  remarks  that  things 
must  be  dififerent  from  the  lime  wlicn  he  was  youngs,  and  that 
children  didn't  wear  glasses  then.  There  is  no  doubt  that 
diseases  of  the  eye  are  on  the  increase,  and  our  present  school 
system,  with  its  increased  demands  upon  the  eyes  and  brains 
of  chiUlrcn  far  hc\-on(l  the  capacity  of  their  _\cars.  can  1)C  justly 
charged  with  a  large  part  of  the  growing  trouble. 

The  eye,  like  any  other  organ,  or  like  any  delicate  instru- 
ment, may  be  abused,  and  the  bad  effects  of  such  abuse  are 
more  noticeable  during  its  growing  period.  The  coats  of  the 
eye-ball  do  not  reach  their  full  firnmess  and  power  of  resistance 
until  about  twenty  years  of  age,  the  time  when  the  rest  of  the 
body  approaches  maturity.  Consequently  before  this  age,  and 
particularly  between  the  ages  of  six  and  sixteen,  during  what 
may  be  called  tl:c  school  years,  the  e_\-e  is  liable  to  injury  from 
overwork.  Thus  is  the  causation  of  myojMa  in  youth  ac- 
counted for.  and  if  ever  "an  ounce  of  prevention  is  worth  a 
pound  of  cure."  it  is  in  the  attention  that  should  be  given  to 
the  eyes  of  growing  children. 

After  twenty  years  of  age  a  good  eye  can  be  abused  in 
many  ways  by  overwork  without  much  danger  of  the  produc- 
tion of  myopia,  although  a  train  of  other  evils  may  result. 
One-fourth  of  the  same  application  of  the  eye  at  the  age  of 
ten,  with  its  walls  and  structures  soft  and  yielding,  would 
cause  its  posterior  wall  to  give  way  and  bring  about  myopia; 
whereas  when  the  eye  is  well  hardened  by  full  growth,  a  much 
greater  amount  of  eye  application  can  be  borne  continuously 
without  the  fear  of  causing  the  walls  of  the  eye-ball  to  bulge 
and  injuriously  changing  the  shape  of  the  organ.  Hence  the 
well-known  fact  that  the  danger  of  the  production  of  myopia 
by  abuse  of  the  eyes,  is  peculiar  to  youth  and  to  its  growing 
state. 

C.W    MV(^PI.\    r.K    CURED? 

The  (|uestion  naturally  arises,  and  it  is  one  that  is  often 
asked  the  optician,  'Ts  there  any  cure  for  myopia?"  The 
answer  to  this  is  unfortunately  always  in  the  negative.  It 
would  scarcely  be  reasonable  to  expect  that  the  dense  and  firm 
fibrous  tissues  forming  the  sclerotic  coat  of  the   eye,  after 


136  MVOPTA. 

liaviiii;-  been  softened  and  extended  and  tliinned  out,  could 
ever  be  returned  to  their  normal  condition  and  position,  so 
that  the  weakened  and  xieldinq  fibres  would  contract  and 
rei:^ain  their  original  tonicity,  and  thus  restore  the  posterior 
part  of  the  sclerotic  to  its  primary  form  and  thickness,  and 
replace  the  retina  again  in  the  position  where  ])arallel  rays  of 
light  would  focus  upon  it  when  the  eye  is  at  rest.  A  little 
reflection  will  show  that  such  a  change  is  impossible. 

But  while  myopia  cannot  be  cured,  much  can  be  done 
to  lessen  its  progress  and  alleviate  its  dangers.  That  by  im- 
proved school  hygiene,  education  of  the  laity,  and  careful  and 
uniform  correction  of  refractive  errors,  it  is  susceptible  of  ma- 
terial mitigation  in  a  community,  has  been  fully  proven  by 
the  careful  and  painstaking  investigations  of  many  oculists 
in  different  cities. 

DOES    AGE    IMPROV]':    THE    M^()I'I(     EYE? 

The  ])opular  notion  that  the  degree  of  myopia  grows  less 
or  is  entirely  neutralized  Avitli  age,  is  far  from  correct.  It 
is  true  that  in  slight  degrees  of  myopia  (as  2  1).  or  less),  the 
inevitable  senile  changes  which  tend  to  diminish  the  refrac- 
tive powers  of  the  dioptric  media,  are  sufficient  for  a  time  to 
neutralize  the  effect  of  the  changed  position  of  the  retina,  and 
enable  such  eyes  to  dispense  with  convex  glasses  for  near 
vision  until  a  very  late  period  of  life. 

In  addition  to  this  the  myope  begins  to  notice  that  he 
does  not  hold  his  book  so  close  as  formerly,  not  because  his 
myopia  is  growing  less  as  might  naturally  be  supposed,  but 
because  the  presbyopic  changes  are  stealing  on  and  his  eye 
is  no  exception  to  the  rule. 

In  myopia  the  focus  of  rays  is  in  front  of  the  retina.  i)artly 
because  of  excessive  refraction  and  partly  on  account  of  the 
length  of  the  eye-ball.  Now  as  the  person  gets  into  middle 
age  the  over-refraction  is  reduced,  and  as  a  consequence  the 
rays  do  not  come  to  a  focus  so  soon,  which  thus  approaches 
the  retina,  the  source  of  the  rays  of  course  remaining  at  the 
same  distance.  P^or  similar  reasons  the  object  may  be  moved 
farther  away  and  the  rays  will  meet  in  focus  at  the  original 
location.     Therefore,  as  age  creeps  on,  the  myope  increases 


MYOPIA.  137 

liis  readiui;'  (lislancc,  usin^'  his  (.'vcs  with  the  same  ease  as  be- 
fore. Not  ])ecausc  the  myopia  has  uiulergonc  improvement, 
Init  on  account  of  the  recession  of  the  near  point  due  to  the 
presence  and  progress  of  ]>resbyopic  chanj^es.  The  actual 
myopia  has  not  l)een  diniinishe(l,  as  shown  by  the  far  point  of 
distinct  vision  remaining  at  the  same  place,  all  the  changes 
and  apparent  improvement  ha\ing  taken  place  in  the  position 
of  the  near  point. 

Tliere  is  one  change  in  the  eye  that  accompanies  age.  that 
does  seem  to  improve  the  vision  of  the  myopic  eye,  and  that 
depends  on  the  size  of.  the  pupil.  As  years  creep  on  the  pupil 
contracts,  sometimes  almost  to  a  pin  point,  thus  cutting  ofif 
some  of  the  circles  of  diffusion  which  are  so  annoying  to  a 
myope  when  looking  at  a  distance,  and  in  this  way  clearing 
the  vision  by  allowing  only  the  central  rays  to  pass,  but  with- 
out in  any  wa\'  intluencing  the  degree  of  nnopia. 

EFjn:tT    OF    lIOLDlXt;   TKK    I'.OOK    FARTHER   AWAY. 

Tlie  attem])t  has  been  made  to  lessen  the  amount  of 
myopia  l)y  recpiiring  the  patient  to  hold  his  book  or  keep  his 
work  at  a  greater  distance,  and  thus  after  a  few  weeks'  prac- 
tice the  myope  is  often  able  to  read  considerably  farther  oft, 
and  he  thinks  that  his  defect  has  diminished;  but  the  experi- 
enced optician  knows  that  he  has  been  holding  his  book  closer 
than  is  really  necessary  (as  all  myopes  are  apt  to  do),  and 
that,  furthermore,  the  degree  of  defect  is  measured  by  the  far 
point  instead  of  the  near  point,  and  that  for  any  distance  less 
than  the  former  the  accommodation  is  brought  into  action. 

Suppose  an  eninietrope  is  accustomed  to  hold  his  book 
twelve  inches  from  his  eyes,  and  by  the  advice  of  some  friend 
he  tries  to  habituate  himself  to  read  at  a  distance  of  sixteen 
inches  instead;  he  simply  reads  with  less  effort  of  accommo- 
dation. 

So  it  is  with  a  myope;  if  he  increases  the  distance  at  which 
his  book  is  ordinarily  held,  he  simply  sees  with  less  exercise  of 
accommodative  power.  No  matter  where  the  reading  is  held, 
the  normal  eye  still  remains  emmetropic  and  the  near-sighted 
eye  is  no  less  myopic,  as  evidenced  by  its  far  point  being  mi- 
changed  in  position. 


138  MYOPIA. 

W'liilc  this  plan  of  treatment  of  holding  the  book  at  the 
greatest  jiossible  distance  does  not  diminish  the  degree  of  the 
myopia,  yet  it  is  most  timely  advice  for  the  myope  to  act 
upon,  and  it  yields  most  excellent  results  in  checking  the  prog- 
ress of  the  organic  changes  taking  place  in  the  fundus  of 
the  eye.  It  lessens  the  amount  of  convergence  needed,  and 
thus  removes  a  great  part  of  the  pressure  of  the  lateral  mus- 
cles on  the  ball,  while  the  erect  position  of  the  head  retards 
the  flow  of  blood  to  the  already  congested  tissues,  and  thus 
restrains  the  softening  processes  upon  which  the  giving  way 
of  the  scleral  tissues  mainly  depend.  Therefore,  the  myope 
should  be  instructed  to  cultivate  the  habit  of  keeping  his  book 
and  work  as  far  from  his  eye  as  possible. 

MYOPIA    NOT    DEPEXDEXT    UPOX    COXVEXITY    OF    THE    CORNEA. 

Formerly  myopia  was  thought  to  be  due  to  an  excessive 
convexity  of  the  cornea,  and  systematic  efforts  were  made  to 
lessen  this  by  compression;  but  now  since  the  defect  is  known 
to  be  dependent  upon  an  extension  of  the  posterior  walls  of 
the  eye,  it  becomes  apparent  that  such  treatment  is  not  only 
useless,  but  injurious,  because  the  pressure  might  have  a  tend- 
ency to  still  further  increase  the  elongation.  jMyopia  then  is 
incurable,  and  only  the  lower  grades  are  neutralized  (and  that 
but  partially)  by  the  compensation  of  senile  changes  during 
the  later  years  of  life.  As  the  eye  then  cannot  be  restored 
to  a  normal  condition,  the  management  must  consist  in  en- 
deavoring to  arrest  the  progress  of  the  abnormal  changes,  and 
at  the  same  time  to  render  vision  easy  and  comfortable  by 
neutralizing  the  error  of  refraction,  as  far  as  it  can  be  done 
without  injury  to  the  eyes,  and  to  increase  the  distance  of  the 
near  point  in  order  to  diminish  the  excessive  convergence  and 
thus  lessen  the  tension  of  the  recti  muscles,  so  as  to  remove 
their  pressure  from  the  ball. 

DISTANT    VISION    I:MPAIRED. 

To  all  near-sighted  persons  distant  objects  appear  as  in  a 
fog,  which  increases  with  the  degree  of  defect  until  even  close 
objects  present  blurred  outlines.  Where  the  myopia  is  but 
slight,  there  is  so  little  inconvenience  that  the  patient  himself 


MYOPIA.  139 

may  not  be  aware  of  liis  defect  until  contrasted  with  the 
sharper  sight  of  some  friend.  On  the  other  hand,  a  highly 
myopic  person  will  be  unable  to  distinguish  the  features  of  a 
person  who  is  no  farther  away  than  three  or  four  feet. 

The  first  intimation  that  a  child's  eyes  are  growing  defec- 
tive comes  in  the  form  of  a  complaint  that  the  blackboard  in 
the  school-room,  which  could  be  clearly  seen  last  year,  is  now 
very  much  blurred  when  viewed  from  the  same  desk,  and  the 
teacher  is  requested  to  allow  a  change  of  seats,  nearer  to  the 
board,  in  order  that  the  letters  and  figures  upon  it  may  be 
visible  to  the  pupil.  A  little  questioning  will  develop  the  fact 
that  the  child  cannot  see  faces  across  the  street  and  cannot 
even  recognize  his  own  parents  at  a  distance. 

Now  that  attention  has  been  called  to  the  matter,  it  is 
noticed  that  in  reading  and  studying  at  home  the  book  is 
held  much  closer  than  formerly.  If  the  parents  themselves 
are  myopic  (as  is  not  unlikely)  they  recognize  the  symptoms 
in  their  child  as  corresponding  with  their  own  myopic  con- 
dition. Probably  then  the  parent  tests  the  child  with  his  con- 
cave lenses,  and  if  distant  objects  are  brought  out  clearly  a 
similar  pair  are  purchased  for  the  child. 

But  this  is  a  very  improper  and  injudicious  thing  for  the 
parent  to  do,  and  it  is  a  well-established  rule  that  concave 
glasses  should  never  be  supplied  to  a  child  except  after  a  most 
careful  and  thorough  examination  by  some  one  especially 
skilled  in  this  line.  It  is  possible  there  may  be  no  myopia  at 
all,  but  only  a  condition  simulating  it,  dependent  upon  a 
spasm  of  accommodation,  and  if  concave  glasses  were  given 
under  such  circumstances  the  eyes  would  suffer  irreparable 
injury. 

Such  a  case  of  spasm  of  the  accommodation  may  present  all 
the  symptoms  of  myopia,  so  much  so  that  even  an  expert  refrac- 
tionist  may  almost  be  misled.  But  if  the  symptoms  ar^  rightly 
interpreted  and  the  condition  early  recognized,  the  danger  of 
a  confirmed  defect  may  be  averted.  Whereas,  if  improperly 
managed,  the  defect  which  at  first  was  only  apparent  becomes 
real  and  the  vision  gradually  grows  worse  and  worse. 


140 


SKfOXD    SIGHT. 

This  term  is  applied  to  those  cases  occurring  in  persons 
of  advanced  years  who  have  been  using-  the  regular  convex 
lenses  for  the  correction  of  their  preslivopia.  and  who  begin 
to  find  that  their  glasses  are  too  strong;  that  they  can  read 
better  with  weaker  ones,  or  perhaps  with  none  at  all.  In 
other  words,  it  is  a  return  of  reading  vision  late  in  life,  and 
persons  of  advanced  years  are  able  to  dispense  with  their  cus- 
tomary convex  lenses.  But  it  should  be  remembered  that 
this  improvement  in  near  vision  is  accompanied  by  a  corre- 
sponding impairment   of   distant  vision. 

The  explanation  of  this  (seemingly  mysterious)  occurrence 
is  as  follows:  Ordinarily  in  old  age  the  crystalline  lens  has 
become  harder  and  denser  and  flatter,  thus  crippling  the  act 
of  accommodation  and  necessitating  the  use  of  convex  glasses 
to  supplement  it.  This  is  a  physiological  change  which  occurs 
in  every  eye  without  exception. 

Now  in  certain  cases  the  lens  commences  to  imbibe  fluid 
and  to  lose  its  dryness  and  hardness.  This  is  accompanied 
by  swelling  of  this  humor,  which  is  made  possible  by  the  elas- 
ticity of  its  capsule.  Then,  instead  of  being  hard  and  flat,  it 
is  soft  and  swollen,  and  having  become  more  convex  it  has 
increased  its  refracting  and  magnifying  pow-er.  This  is  the 
first  step  in  the  formation  of  cataract,  although  for  many 
months  and  even  years  the  lens  may  retain  its  transparency, 
even  though  altered  in  shape  and  consistency.  But  sooner 
or  later  opaque  streaks  or  spots  begin  to  make  their  appearance 
in  it,  and  gradually  the  whole  lens  loses  its  clearness,  and 
W'hen  it  has  become  entirely  opacjue  the  condition  is  known 
as  cataract. 

The  statement  has  been  made  that  when  second  sight 
makes  its  appearance  before  seventy,  it  foreshadows  blindness 
from  cataract  in  a  comparatively  short  time — perhaps  in  six 
months,  certainly  within  a  few  years. 

When  the  privilege  of  second  sight  first  makes  its  appear- 
ance in  extreme  old  age,  that  is  in  persons  of  eighty  years  and 
upward,  the  pathological  changes  in  the  lens  are  not  likely 
to  progress  very  rapidly,  and  the  eyes  will  probably  last  as  long 


MVoriA.  141 

as  the  patient  does,  because  the  debihty  of  old  age  is  apt  to 
prove  fatal  before  the  opacity  in  the  lens  has  made  sufficient 
advance  to  restrict  the  sight. 

Concave  lenses,  for  a  longer  (jr  shorter  lime,  will  iiii])rove 
the  distant  vision  in  these  cases,  just  as  in  regular  myopia, 
while  reading  may  be  possil)le  without  any  glasses.  But  after 
a  time,  as  the  degeneration  in  the  lens  substance  progresses, 
the  passage  of  light  to  the  retina  is  impeded  and  obstructed, 
and  then  vision  becomes  impaired  both  near  and  far,  and 
glasses  are  no  longer  of  any  assistance. 

TIIK  FAR   POIXT  Till':  MKASl'RE  OF  Till-;   MYOPIA. 

The  distance  of  the  far  pcjint  re])resents  very  closely  the 
grade  of  the  myopia,  and  therefore  in  order  to  save  time  and 
to  quickly  determine  the  approximate  glass  required  in  any 
case  of  myopia  under  examinatioii,  without  going  through  the 
process  of  trying  a  great  many  different  numbers  of  glasses,  a 
procedure  both  tedious  to  the  patient  and  tiresome  to  the  op- 
tician, the  far  point  can  be  soon  located  and  the  extent  of  the 
defect  at  once  becomes  apparent. 

The  patient  is  recjuested  to  read  small-sized  print,  not 
necessarily  the  finest  on  the  reading  card,  but  somewhat 
smaller  than  the  letters  on  this  page,  while  the  card  is  slowly 
moved  away  to  the  farthest  distance  from  the  eyes  at  which 
the  letters  still  remain  legible.  If  the  myopia  be  of  high  de- 
gree and  the  near  point  very  close  to  the  eyes,  the  very  smallest 
print  can  be  used.  If  ten  inches  is  found  by  this  means  to  be 
the  far  ])oint,  then  4  I),  is  the  ai)])n).\imate  measure  of  the 
myopia  and  a  concave  lens  of  that  number  is  the  i)roper  cor- 
rection, or  nearly  so. 

In  order  to  determine  if  such  glass  is  the  one  that  ought 
to  be  prescribed,  it  is  placed  before  the  eye  of  the  patient,  who 
is  requested  to  look  at  the  test-card,  hanging  twenty  feet  away, 
and  read  the  lowest  line  he  can  make  out;  and  then  by  trying 
alternately  weak  convex  and  weak  concave  lenses,  placed  be- 
fore the  original  glass,  the  proper  number  is  soon  determined. 

If  the  —  4  D.  lens  affords  a  vision  of  |o,  a  +  .25  D.  is 
placed  before  it.  and  if  the  No.  20  line  still  remains  legible, 
then  a  -^  .50  I),  is  tried.     If  this  dulls  the  vision  (juite  notice- 


142  MYOPIA. 

ably,  then  the  —  4  D.  lens  reduced  by  the  +  .25  D.  would  be 
the  proper  correction,  and  the  prescription  would  be  —  3.75 
D..  because  the  rule  in  myopia  is  to  order  the  very  weakest 
glass  with  which  satisfactory  vision  is  possible. 

If,  however,  the  —  4  D.  lens  does  not  raise  the  acuteness 
of  vision  to  f^,  then  a  —  .25  D.  is  placed  before  it;  this  im- 
proves vision  slig-htly,  but  still  it  is  not  up  to  the  normal 
standard.     Then  a  —  .50  D.  is  tried,  and  this  brino^s  out  the 


(Oe  Wccker  and  Fuchs.) 
The  Posterior  Staphyloma  of  Myopia,  show- 
ing not  only  the  white  crescent  around  the 
optic  disc,  but  also  white  patches  of  atrophic 
choroiditis  in  the  region  of  the  yellow  spot, 
and  general  exposure  of  the  choroidal  vessels 
by  absorption  of  the  retinal  pigment  epithe- 
lium. 

No.  20  line  clearly,  every  letter  being  sharp  and  distinct.  This 
proves  that  the  first  lens  is  not  quite  sufficient  to  entirel\" 
correct  the  refractive  error,  and  a  higher  number  must  be  sub- 
stituted, which  we  have  found  to  be  —  4.50  D. 

EXPLAXATIOX  OF  THE  FAR  POINT. 

The  myopic  eye  is  at  rest  when  adjusted  for  its  far  point, 
just  as  an  emmetropic  eye  is  at  rest  when  adjusted  for  infinite 
distance ;  the  divergent  rays  from  the  far  point  in  the  first  case, 
and  the  parallel  rays  from  infinity  in  the  second  case,  being 


MYOPIA.  143 

each  focused  on  the  retinae  of  their  respective  eyes  without 
any  effort  of  accommodation. 

Now,  when  a  concave  lens  of  the  projaer  focal  distance  is 
placed  before  the  eye,  the  rays  that  pass  through  it  from  a 
distance  will  assume  the  same  divergence  as  if  they  proceeded 
from  the  far  point,  and  hence  will  be  exactly  focused  upon  the 
retina  in  the  same  way.  Therefore,  the  parallel  rays  from  a 
distance,  after  having  been  made  artificially  divergent,  will 
afford  distinct  vision  of  the  remote  objects  from  which  they 
proceed;  just  as  in  the  case  of  the  naturally  divergent  rays  from 
a  close  point,  which  enable  near  objects  to  be  clearly  seen. 

This  will  explain  why  a  far  point  of  ten  inches  indicates  a 
myopia  of  4  D.,  and  why  a  concave  lens  of  the  latter  strength 
will  correct  the  defect,  and  is  a  beautiful  illustration  of  the 
adaptation  of  the  refractive  properties  of  lenses  to  the  correc- 
tion of  the  errors  of  refraction  of  the  human  eye. 

WIIV  MYOPIC  EYES  ARE  REGARDED  AS  STRON'G  EYES. 

There  is  a  widely  prevalent,  popular  notion  that  the  eye 
of  the  myope  is  superior  in  strength  to  any  other  form  of  eye- 
ball. Notwithstanding  the  statement  that  has  already  been 
made  that  such  an  eye  is  a  diseased  eye,  there  is  some  founda- 
tion for  this  idea  to  become  fixed  in  the  public  mind,  in  that 
the  myope,  more  readily  than  the  emmetrope.  can  distinguish 
minute  objects,  in  the  examination  of  which  he  is  able  to  bring 
them  much  closer  to  his  eyes,  just  as  an  emmetrope  would  be 
compelled  to  place  a  magnifying  glass  before  his  eye  for  the 
same  purpose. 

This  proximity  increases  the  size  of  the  image  formed  on 
the  retina  as  well  as  the  quantity  of  light  reflected  upon  it,  and 
as  a  consequence  vision  is  made  much  more  distinct.  The 
dilated  pupil,  which  is  common  in  myopia,  allows  of  a  still 
further  increase  in  the  illumination. 

If  an  optical  student  (who  is  emmetropic)  desires  to  test 
for  himself  the  supposed  superiority  of  the  myopic  eye,  he  can 
make  himself  artificially  near-sighted  by  placing  before  his 
eyes  a  convex  lens;  in  this  way  an  addition  is  made  to  the  re- 
fractive power  of  the  eye,  parallel  rays  are  brought  to  a  focus 
in  front  of  the  retina,  distant  vision  is  verv  nuich  blurred,  and 


144  MvoriA. 

even  near  vision  is  not  entirely  satisfactory.  Such  an  experi- 
ment will  tend  to  demonstrate  the  fact  that  the  apparent  supe- 
riority of  the  myopic  eye  is  more  fancied  than  real,  except  in 
slight  degrees  (2  D.  or  3  1).  or  less). 

In  these  latter  cases  it  is  not  uncoininon  to  find  many  per- 
sons who  are  utterly  unconscious  of  any  defect  in  their  sight. 
Not  having-  an\  sjjccial  need  for  sharp  distant  vision,  they  walk 
along  the  streets  without  a  suspicion  that  others  can  see  better 
than  themselves.  Only  a  few  moments  ago  the  writer  had 
an  illustration  of  this  fact  in  his  own  office:  a  lady  had  com- 
pound myopic  astigmatism  and  a  visual  acuteness  of  only  j%%. 
Very  naturally  and  properly  we  suggested  glasses  for  constant 
wear  and  to  improve  distant  vision.  The  lady  indignantly  re- 
pelled the  suggestion,  and  going  to  the  window  she  pulled 
aside  the  lace  curtain  and  triumphantly  exclaimed:  "l  don't 
need  glasses  for  distant  vision;  1  can  see  those  numbers  on  the 
doors  (they  were  very  large),  and  if  I  was  acquainted  with 
those  people  I  could  recognize  every  one  of  them.  My  sight 
is  all  right;  all  1  need  is  glasses  for  reading."  Such  a  remark 
seemed  ridiculous  from  a  patient  whose  acuteness  of  vision 
was  only  ^W,  but  she  w^as  so  determined  that  it  seemed  useless 
to  argue  with  her. 

PROGESSni-:   .MYOPIA. 

Myopia  is  a  defect  which  does  not  decrease  in  degree;  in 
fact,  it  even  does  not  usually  remain  stationary,  but  its  natural 
tendency  is  to  increase.  Such  a  condition  is  more  than  a 
simple  error  of  refraction ;  it  is  really  a  disease,  and  one  that  is 
fraught  with  many  dangers  to  the  eye. 

The  optical  characteristic  of  a  myopic  eye  is  that  the  posi- 
ti(jn  of  the  retina  is  behind  the  focus  of  parallel  rays;  its 
anatomical  and  pathological  characteristic  is  that  this  departure 
of  the  retina  from  its  normal  condition  is  due  to  a  distention  of 
the  eye-ball,  caused  by  a  giving  way  of  the  coats  of  the  ball  at 
the  fundus.  As  the  membranes  thus  become  attenuated,  their 
power  of  resistance  is  at  the  same  time  diminished;  in  the  face 
of  this  fact  it  is  hardly  to  be  expected  that  the  trouble  would 
remain  stationary,  when  all  the  conditions  are  favorable  for  its 
increase.  As  the  distention  grows  the  myopia  progresses,  de- 
pendent upon  a  real  disease  of  the  eye. 


MVoriA. 


Ho 


On  account  of  the  elongation  of  the  niyopic  eye-hall  in  its 
antero-posterior  diameter,  rcsenihling  somewhat  the  shape  of 
an  egg,  its  very  form  causes  it  to  sufifer  its  greatest  pressure 
backward,  niis  fact,  together  with  that  mentioned  above 
(thinning  of  the  coats  of  the  eye  and  diminished  power  of  re- 
sistance), will  account  for  the  progressive  tendency  of  myopia. 

Of  course,  it  can  be  easily  understood  that  the  higher  the 
degree  of  myopia  the  more  likely  it  is  to  assume  the  progressive 
form,  even  in  more  advanced  years;  while  in  youth  almost 
every  case  of  myopia  shows  a  tendency  to  be  progressive,  and 
this  is  really  the  critical  period  for  the  myopic  eye. 

The  temi  progressive  myopia  is  reserved  for  those  cases 
where  the  defect  increases  rapidly  and  is  accompanied  by 
symptoms  of  congestion  and  irritation,  and  does  not  apply  to 
those  cases  where  the  progress  of  the  defect  is  very  slow  and 
where  the  eye  is  free  from  all  unpleasant  symptoms. 

POSTERIOR   .STAPHYLOMA. 

The  general  acceptance  of  posterior  staphyloma  as  the 
anatomical  basis  of  myopia  rests  upon  two  factors: 

1.  Descriptions  of  myopic  eyes  after  death. 

2.  Ophthalmoscopic  examinations  during  life. 

Myopic  eyes  of  low  or  medium  degrees  (such  as  are 
usually  acquired  during  school  life)  do  not  present  this  con- 
dition of  posterior  staphyloma,  but  it  is  always  found  in  eyes 
having  a  myopia  exceeding  lo  D. 

Tlie  axial  diameter  of  a  normal  eye  is  about  23  mm.,  which 
is  considerably  increased  by  the  presence  of  posterior  staphy- 
loma; of  the  recorded  cases  the  shortest  measured  27  mm.  and 
the  longest  32  mm.  corresponding  respectively  to  a  myo])ia 
of  II  D.  and  of  20  D. 

As  the  thinning  of  the  w^alls  of  the  eye  in  these  cases 
usually  extends  forward,  the  transverse  diameter  is  also,  as  a 
rule,  greater  than  normal,  ranging  from  24^  mm.  to  28  mm., 
as  compared  with  22  mm.  to  23  nmi.,  the  normal  measure. 

The  ophthalmoscopic  appearances  of  posterior  staphyloma 
are  marked  and  unmistakable.  The  characteristic  symptom  is 
a  white  crescent  at  the  edge  of  the  optic  disk,  generally  at  the 
outer  side.     This  crescent  varies  greatlv  in  size,  from  a  small 


14G  MYOl'IA. 

arc  to  a  large  zone,  and  may  extend  all  art)und  the  disk,  and 
even  encroach  on  the  region  of  the  yellow  si>ot,  its  greatest 
extent  being  always  in  this  direction.  Its  edges  may  be 
sharply  and  distinctly  defined,  or  may  be  irregular  and  gradn- 
allv  merge  in  the  surrounding  healthy  structure. 

There  may  be  patches  of  pigment  about  the  margin  of 
the  white  crescent,  or  scattered  over  its  surface.  The  crescent 
itself  is  of  a  brilliant  white  color,  which  makes  the  disk  by 
contrast  appear  abnormally  pink.  On  acount  of  this  white- 
ness of  the  background,  the  small  blood-vessels  that  pass 
over  it  are  rendered  more  visible  and  are  more  easily  dis- 
cerned than  elsewhere  on  the  retina.  The  whiteness  is  due 
to  a  thinning  and  an  atrophy  of  the  substance  of  the  choroid, 
which,  indeed,  may  be  found  entirely  lacking  at  this  spot, 
thus  allowing  the  glistening  sclerotic  to  come  into  view. 
Hence  the  white  crescent  is  simply  a  portion  of  the  sclerotic, 
which,  for  the  reasons  mentioned  above,  becomes  abnormally 
visible. 

On  account  of  the  wasting  of  the  choroid  there  is  an 
absence  of  the  pigment  cells,  and  this  removal  of  the  natural 
protection  against  excessive  light  gives  rise  to  the  sense  of  glare 
which  such  patients  frequently  complain  of.  As  might  be 
expected  from  this,  the  sight  of  these  myopes  is  often  much 
improved  by  a  tinted  glass,  which,  under  the  circumstances, 
is  not  only  allowable  but  advisable. 

DEGREE   OF   MYOPIA. 

The  writer  has  frequently  asked  the  following  question 
of  his  optical  students,  "Upon  what  does  the  degree  of  myopia 
depend?"  and  the  almost  invariable  answer  has  been,  "The 
distance  of  the  far  point."  This  shows  an  incorrect  concep- 
tion of  the  point  involved.  The  location  of  the  far  point  simply 
indicates  or  represents  the  amount  of  the  myopia,  which  de- 
pends upon  the  distance  of  the  focus  of  parallel  rays  in  front 
of  the  retina.  The  nearer  the  focus  is  to  this  membrane  the 
lower  the  degree  of  defect;  the  farther  the  focus  is  removed 
from  it,  the  higher  the  grade  of  myopia. 

This,  distance  of  the  focus  cannot  be  directly  estimated, 
but  can  be  determined  indirectly  by  measuring  the  excess  of 


MYOPIA.  147 

refractive  power.  When  tlie  refraction  of  the  eye  exactly  cor- 
responds with  the  lengtli  of  the  optic  axis,  the  condition  is 
on'i  of  emmetropia;  when  the  former  exceeds  the  latter,  the 
eye  is  known  as  a  myopic  one,  and  the  concave  lens  that 
neutralizes  the  surplus  will  indicate  the  grade  of  myopia. 
Suppose  a  —  4  D.  lens  is  required:  this  proves  that  there  is 
a  myopia  of  4  D.,  and  that  there  is  an  excess  of  refractive 
power  of  4  D.,  which  causes  parallel  rays  to  focus  in  front  of 
the  retina.  The  concave  lens  diminishes  the  refraction  of  the 
eye  and  gives  to  parallel  rays  sufficient  divergence  to  throw 
their  focus  back  upon  the  retina  and  thus  afford  clear  vision. 

APPARENT    OR    ACCOMMODATIVE    MYOPIA. 

The  attention  of  the  optician  should  be  called  to  a  condi- 
tion of  apparent  or  false  myopia,  which  is  not  myopia  at  all, 
but  is  made  to  simulate  it  on  account  of  a  spasm  of  the 
accommodation,  by  means  of  which  the  refraction  of  the  eye 
is  increased  and  parallel  rays  are  brought  to  a  focus  in  front 
of  the  retina. 

Ordinarily  the  ciliary  muscle  acts  just  sufficiently  to  focus 
divergent  rays  on  the  yellow  spot  and  to  adjust  the  eye  for 
the  every-day  purposes  of  close  vision.  But  this  little  muscle 
may  fall  into  a  condition  of  abnormal  activity,  known  as 
spasm  of  the  accommodation,  where  the  muscle  refuses  to 
relax  and  continues  indefinitely  to  keep  the  eye  in  a  condition 
of  over-refraction.  This  is  the  optical  condition  present  in 
myopia,  and  gives  rise  to  all  the  symptoms  of  this  defect. 
This  ciliary  spasm  may  occur  in  emmetropia  or  more  often  in 
hypermetropia,  as  explained  in  the  last  chapter,  where  we 
gave  warning  of  the  danger  of  mistaking  hypermetropia  for 
myopia. 

Spasm  of  the  acconnnodation  is  of  more  frequent  occur- 
rence than  is  generally  supposed,  and  in  addition  to  the  appar- 
ent myopia  which  it  causes,  also  gives  rise  to  marked  symp- 
toms of  asthenopia  during  reading  or  close  work.  The 
pupil  is  contracted  and  the  ophthalmoscope  will  sliow  con- 
gestion of  the  optic  disk  and  retina. 

When  the  vision  of  such  a  patient  is  tested  with  the 
trial  lenses  there  will  be  noticeable  variations  in  tlie  appar- 


14S  MYOI'IA. 

cut  refraction:  sonictinus  lie  will  prefer  one  glass,  some- 
times another.  When  the  amplitude  of  accoiiimodation 
is  measured  there  will  be  (juite  a  discrepancy  between 
the  i>osition  of  the  far  point  and  the  degree  of  apparent 
myopia.  I'or  instance,  the  location  of  the  far  point  may  be 
ten  inches  from  the  eye,  which  would  lead  to  a  suspicion  of  a 
myopia  of  4  D.  But  when  the  acuteness  of  vision  is  taken, 
such  an  error  would  be  at  once  discovered.  The  patient  can 
read  all  the  letters  on  the  test  card,  and  only  a  weak  concave 
lens  is  required  (perhaps  —  i  D.)  to  raise  the  vision  to  the 
normal  of  .?[}.  ]n  this  way  the  diagnosis  between  real  myopia 
and  apparent  m}opia  due  to  spasm  can  often  be  made. 

The  fact  should  not  be  overlooked  that  spasm  of  the 
ciliary  nniscle  may  be  dependent  upon  an  insufificiency  of  the 
internal  recti  muscles.  The  excessive  muscular  effort  required 
to  maintain  the  necessary  degree  of  convergence  carries  with 
it  an  extreme  contraction  of  the  ciliary.  Just  as  in  hyperme- 
tropia  the  extra  accommodation  causes  an  extra  convergence 
which  may  result  in  convergent  strabismus:  in  both  instances 
produced  by  the  close  relation  which  naturally  exists  between 
the  functions  of  accommodation  and  convergence.  In  these 
cases  a  pair  of  prisms,  bases  in,  may  assist  in  relaxing  the 
ciliary  spasm. 

Spasm  of  accommodation  is  most  apt  to  occur  in  nervous 
individuals,  when  the  system  is  enfeebled  or  the  nervous  force 
exhausted;  and,  strange  to  say,  the  degree  of  spasm  bears 
no  relation  to  the  vigor  of  the  ciliary  muscle.  In  fact,  it  is 
usually  found  in  connection  with  a  weakened  accommodation, 
and  instead  of  being  an  evidence  of  extra  strength,  must  be 
regarded  as  an  indication  of  nervous  debility.  This  is  proven 
by  the  fact  that  eyes  exhausted  by  overwork  are  the  ones 
that  are  subject  to  spasm,  and  the  accompanying  asthenopia 
tends  tO'  increase  the  spasmodic  action. 

The  treatment  of  cases  of  spasm  of  accommodation  will 
oftentimes  tax  the  skill  and  ingenuity  of  the  optician.  One 
method  of  management  consists  in  the  use  of  convex  lenses, 
a  moderately  strong  pair  for  reading  and  a  weak  pair  for 
distance.  As  is  well  known,  the  use  of  the  convex  lenses  con- 
stantly and  persistently  encourages  a  relaxation  of  the  spasm. 


MYOl'IA.  HH 

and  the  patient  who  was  apparently  near-sighted,  is  soon  able 
to  read  the  No.  20  line  without  the  concave  glasses  that  were 
formerly  necessary. 

Of  course,  the  wearing  of  convex  lenses  in  this  way  makes 
vision  indistinct,  and  the  patient  is  apt  to  rebel.  Sometimes, 
with  intelligent  persons,  if  the  rationale  of  the  treatment  is  ex- 
plained, their  cooperation  may  be  secured.  But  if  not,  the 
distance  glasses  may  be  dispensed  with  and  reliance  placed 
on  the  reading  glasses,  to  which  very  few  persons  will  object. 

In  some  stubborn  cases  it  may  become  necessary  to  in- 
voke the  services  of  a  physician,  and  place  the  eyes  under  the 
influence  of  atropine,  which  may  need  to  be  continued  for 
several  weeks  before  the  spasm  is  overcome  and  the  ciliary 
muscle  completely  paralyzed.  Then  the  exact  condition  of 
the  refraction  can  be  determined,  and  if  hypermetropic,  as  it 
often  is,  the  correcting  convex  glasses  should  be  prescribed 
at  once  and  the  patient  directed  to  wear  them  and  become 
accustomed  to  them  while  the  muscle  is  recovering  from  the 
eflfects  of  the  drug. 

SYMPTOMS    OF    MYOPIA. 

The  two  principal  symptoms  are  the  impairment  of  dis- 
tant vision  and  the  improvement  of  close  vision.  The  eyes 
are  usually  large,  full  and  prominent,  and  the  pupils  dilated, 
although  as  age  creeps  on  they  gradually  contract,  thus 
diminishing  the  circles  of  diffusion  and  slightly  improving 
vision.  1  he  young  myope  makes  use  of  the  same  principle 
to  assist  vision  by  half-closing  his  lids,  which  habit  indeed  is 
so  characteristic  of  this  defect  as  to  give  occasion  for  its  name, 
the  word  myopia  originating  from  two  Greek  words,  meaning 
"to  close  the  eyes." 

On  account  of  the  impairment  of  distant  vision,  myopes 
are  inclined  to  avoid  out-door  sports,  and  rather  prefer  in- 
door amusements,  as  reading,  drawing,  etc.,  which  do  not  re- 
quire good  vision  at  a  distance.  But,  unfortunately,  such 
habits  cause  congestion  of  the  eyes,  and  thus  favor  the  in- 
crease of  myopia.  Of  course,  where  the  correcting  glasses  are 
worn  early  in  life,  the  boy  has  his  range  of  vision  widened. 
and  in  this  respect  is  placed  on  an  equality  with  his  com- 


150  MYOPIA, 

panions,  and  then  he  lias  tlic  same  desire  as  they  to  join  in  all 
their  games. 

In  progressive  forms  of  myopia  the  field  of  vision  may 
be  limited  and  besides  show  numerous  blank  spots,  on  account 
of  patches  of  retinal  atrophy. 

In  some  cases  of  myopia  there  may  be  evidences  of  con- 
siderable irritation  of  the  eyes,  especially  after  using-  them  by 
artificial  light  for  any  great  length  of  time.  The  conjunctiva 
may  be  blood-shot  and  the  lids  red,  while  the  patient  com- 
plains of  pain,  sensitiveness  to  light,  a  feeling  of  eye-strain, 
eye-balls  sore  to  the  touch,  and  the  annoying  "muscae  voli- 
tantes,"  which  have  already  been  described. 

The  symptoms  of  myopia  that  have  been  enumerated  are 
both  subjective  and  objective,  the  former  depending  on  the 
visual  sensations  of  the  patient,  and  the  latter  on  what  the 
optician  himself  observes. 

PREVENTION  OF  MYOPIA. 

The  importance  of  the  prevention  of  myopia  cannot  be 
too  forcibly  impressed  upon  parents,  teachers  and  school 
directors,  in  order  that  the  conditions  which  cause  it  may  be 
understood  and  removed.  This  is  an  age  of  prevention  rather 
than  cure.  Everywhere  efforts  are  made  to  prevent  disease 
and  all  questions  pertaining  to  hygiene  and  sanitary  reform 
receive  the  closest  study  and  attention.  The  prevention  of 
small-pox,  diphtheria,  yellow  fever,  cholera  and  tuberculosis 
is  enforced  by  law,  and  is  facilitated  by  laboratory  work  with 
the  microscope  and  test  tube.  This  certainly  shows  the  un- 
selfish interest  physicians  manifest  in  the  welfare  of  mankind, 
because  it  is  evident  that  the  existence  of  disease  is  more  profit- 
able to  the  medical  profession  than  its  absence;  but  the  dis- 
covery of  a  prophylactic  measure  affords  more  satisfaction  to 
a  physician  than  a  new  method  of  cure. 

The  optical  profession  should  measure  up  to  the  same 
standard,  and  should  exhibit  the  same  commendable  spirit 
in  developing  measures  of  hygienic  reform  as  it  pertains  to  the 
eye,  and  in  educating  the  public  along  the  same  lines.  The 
scope  of  this  book  will  not  permit  an  extended  reference  to 
this  subject  or  a  complete  description  of  the  work  that  has 


MYOPIA.  1-'>1 

been  and  should  be  done  in  this  field,  but  a  brief  mention  of 
some  of  the  practical  points  bearing  on  the  prevention  of 
myopia  is  at  least  necessary. 

Consideration  must  be  given  to  those  conditions  of  school 
life  which  tend  to  develop  this  defect;  and  the  first  thought 
that  arises  is  that  children  should  not  be  sent  to  school  unless 
their  general  health  is  robust  enough  to  endure  the  strain.  In 
addition,  the  refraction  of  the  eye  should  be  examined,  as 
well  to  detect  any  possible  defect  as  to  determine  their  capac- 
ity for  the  work  on  which  the  child  is  just  entering.  The  im- 
portance of  this  latter  procedure  as  a  prophylactic  measure 
will  commend  itself  at  once  to  those  interested  in  the  welfare 
of  children's  eyes. 

LIGIITIXC,  OF  SCHOOL   ROOMS. 

The  school  building  should  be  lighted  sufficiently  and 
properly,  and  should  also  be  so  constructed  as  to  aflford  the 
pupils  all  the  advantages  possible  in  the  way  of  location,  ven- 
tilation, sanitary  plumbing,  pure  and  abundant  water,  etc. 
The  light  in  the  school  room  should  be  direct,  and  not  re- 
flected from  the  walls  of  adjoining  buildings. 

Light  that  is  insufficient  or  ill-arranged  is  the  most  poten- 
tial factor  in  the  causation  of  myopia  in  the  sch(X)l  room, 
because  such  light  compels  a  lessening  of  the  distance  between 
the  eye  and  the  book  when  reading  or  writing,  and  therefore 
the  question  of  proper  light  becomes  an  all-important  one. 

The  light  should  be  sufficient  in  quantity,  should  come 
from  above  the  level  of  the  eyes,  and  as  far  as  possible,  should 
fall  upon  the  desk  from  the  left-hand  side.  This  arrangement 
of  light  could  be  best  secured  if  the  school  rooms  were  of  an 
oblong  shape,  all  the  windows  located  in  one  of  the  long  sides, 
the  desks  placed  in  rows  at  right  angles  to  this  wall,  and  the 
scholars  facing  that  end  of  the  room  which  allows  the  light 
to  fall  from  the  left.  The  windows  should  extend  upward  to 
the  ceiling,  starting  about  four  feet  from  the  floor.  The  total 
window  surface  should  be  (^ne-fifth  of  the  floor  area,  with  the 
panes  as  large  as  possible. 

It  would  be  better  if  the  education  of  children  could  be 
carried  on  entirely  by  daylight,  but  in  cloudy  weather,  in  the 


afternoons  of  the  short  days  in  mid-winter,  and  in  ni^ht 
schools,  artificial  illumination  becomes  a  necessity.  The  usual 
naked  gas  jets  are  mentioned  only  to  be  condemned.  The  im- 
proved Welsbach  burners  afford  an  excellent  liqht.  and  if 
properly  placed  over  the  children's  heails  and  in  sufficient 
numbers,  would  constitute  a  satisfactory  metho<l  of  artificial 
illumination.  If  electricity  is  available  for  introduction  into 
the  building,  the  incandescent  light  is  perhaps  the  best  substi- 
tute for  daylight.  It  is  capable  of  luiiform  distribution  and 
concentration,  and  does  not  heat  or  vitiate  the  atmosphere. 
The  lights  should  be  ample  in  ntnnber,  i)ro])erly  shaded  and 
brought  close  enough  to  the  desk  tt)  afford  an  alnuidant 
illumination. 

SCHOOL  DESKS  AND  SEATS. 

In  addition  to  the  proper  lighting  of  the  school  room,  the 
question  of  the  construction  of  desks  and  seats  is  one  of  no 
little  importance,  as  it  doubtless  is  partly  responsible  for  the 
increasing  percentage  of  myopia  found  in  school  children,  and 
certainly  improper  seats  and  desks  produce  injurious  results 
upon  the  health  of  the  children,  particularly  affecting  their 
lungs,  abdominal  organs,  spine  and  figure. 

jV  crooked  and  stooping  posture  cannot  always  be  blamed 
upon  tlie  pupil,  because  for  anatomical  and  phvisological 
reasons  it  is  imjjossible  for  a  child  to  assume  and  maintain  a 
good  posture  with  unsuitable  seats  and  desks.  The  faults 
may  be  enumerated  as  follows: 

1.  Improper  backs  or  no  backs. 

2.  Too  great  distance  between  seat  and  desk. 

3.  Disproportion  between  height  of  seat  and  of  desk. 

4.  Unsuitable  form  and  slope  of  desk. 

This  naturally  leads  to  a  brief  mention  of  the  essentials  in 
proper  school  furniture.  The  scat  must  be  of  such  height 
as  to  allow  the  feet  to  rest  upon  the  floor,  which  is  accom- 
plished by  adjustable  seats  and  measuring  the  distance  from 
the  sole  of  the  foot  to  the  inner  bend  of  the  knee.  The  seat 
should  be  generously  wide,  slightly  concave,  but  without  any 
inclination,  and  its  front  edge  about  two  inches  under  the  edge 
of  desk.     Some  authorities  consider  this  overlapping  of  the 


MYOPIA.  l->3 

desk  as  unnecessary,  clainiin.q-  that  the  edg^c  of  desk  and  of  seat 
should  be  on  same  plane. 

The  seats  should  have  comfortable  backs,  corresiX)nding 
in  size  to  the  heig^ht  of  pupil.     They  must  not  be  too  high. 


Showing  the  improper  position  assumed  by  the 
pupil  because  the  seat  and  desk  is  too  low,  and  the 
edge  of  the  desk  is  too  far  in  front  of  the  seat. 
The  child  Is  compelled  to  sit  on  the  front  of  the 
seat,  the  body  falls  forward  and  finds  support  upon 
the  elbows,  which  rest  upon  the  desk.  In  writing, 
the  left  arm  is  used  for  support  while  the  right 
hand  is  employed,  which  causes  the  vertebral 
column  to  be  partially  turned  upon  its  long  axis 
and  the  body  to  be  placed  in  a  distorted  position. 
The  head  falls  forward  toward  the  work  and  turns 
to  the  right;  this  brings  the  face  too  near  to  the 
page,  the  left  eye  closer  than  the  right.  The 
normal  relation  between  the  plane  of  the  face  and 
the  work  is  thus  disturbed,  while  the  abnormal 
near  point  adds  greatly  to  the  strain  upon  the  ac- 
commodation and  convergence. 

coming-  only  far  enough  to  support  the  shoulders  and  leave  the 
head  free  to  assume  the  proper  position.  The  top  of  the  desk 
must  be  just  high  enough  to  allow  the  elbow  to  rest  upon  it 
without  displacing  the  natural  position  of  the  shoulder. 


154  MYOPIA. 

In  order  to  meet  all  the  requirements,  it  is  evident  that 
the  size  of  the  desk  and  seat  should  correspond  to  the  size  of 
the  pupil.  But  it  is  equally  obvious  that  a  desk  rigidly  con- 
structed for  all  the  pupils  of  a  certain  grade  or  a  certain  age. 


Showing  the  correct  position  \\hich  the  student 
should  assume,  the  lower  part  of  back  and  pelvis 
being  supported  by  the  forward  curve  in  the  bade 
of  the  seat.  The  forearm  of  the  pupil  rests  lightly 
upon  the  desk,  which  is  not  so  high  as  to  raise  the 
shoulders,  but  sufficiently  high  to  avoid  the  neces- 
sity of  stooping  in  order  to  reach  it.  Both  the 
desk  and  seat  are  adjustable  in  height  by  means  of 
the  nuts  on  the  pedestal  of  each.  The  front  edge 
of  the  seat  projects  an  inch  or  two  under  the  desk, 
which  allows  the  correct  upright  sitting  posture  to 
be  assumed  and  maintained,  and  in  fact  the  child 
finds  it  easier  to  sit  in  this  position  than  in  any 
other  he  can  assume. 

would  fall  short  of  answering  the  purpose  on  account  of  ex- 
tremes in  size  which  may  exist.  Therefore  it  is  not  only 
necessary  to  have  desks  and  seats  of  different  sizes  for  the 
various  grades,  but  they  should  also  be  easily  adjustable  to 


MYOPIA.  155 

meet  the  requirements  of  each  pupil  in  tliat  particular  grade. 
After  the  seat  and  desk  has  been  adapted  to  the  length  of  the 
leg  and  height  of  body  the  adjustment  must  be  fixed  by  a  key 
which  should  be  in  the  hands  of  the  teacher,  so  as  not  to  allow 
of  any  alteration  by  the  pupil  himself. 

INCLINATION  OF  TOP  OF  DESK. 

The  reasons  given  why  the  top  of  the  desk  should  slope 
are  so  interesting  and  important  from  a  physiological  and 
hygienic  standpoint  for  the  benefit  of  adults  as  well  as  children, 
that  the  optician  should  not  be  lacking  in  the  knowledge  which 
is  therein  implied. 

The  eyes  are  moved  in  dilYerent  directions  by  six  muscles. 
The  movements  of  the  two  eyes  are  associated,  and  only  cer- 
tain sets  of  muscles  of  both  eyes  can  be  brought  into  simul- 
taneous action.  For  instance,  we  cannot  turn  one  eye  up  and 
the  other  down,  but  we  can  only  move  both  eyes  at  the  same 
time  in  the  same  direction,  either  up  or  down.  We  can  use 
both  internal  recti  muscles  in  the  act  of  convergence,  but  we 
cannot  use  the  two  external  recti  muscles  and  turn  the  eyes 
from  parallelism  to  divergence.  We  can  use  the  internal 
rectus  muscle  of  one  eye  with  the  external  rectus  of  the  other, 
as  when  the  eyes  are  turned  to  the  right  or  left. 

Of  the  various  combinations  of  muscles,  some  can  be 
comfortably  kept  in  action  for  a  length  ol  time,  others  only  for 
a  few  seconds.  Thus  it  requires  considerable  effort  to  con- 
verge the  eyes  and  look  upward  at  the  same  time;  wliile,  on  the 
other  hand,  we  can  converge  and  look  downward  with  ease. 
If  we  want  to  see  distinctly  a  line  or  a  plane,  instead  of  a  point, 
a  particular  turning  of  both  retinae  is  necesary  for  each  position 
of  the  object.  When  this  turning  can  be  produced  by  a  com- 
bination of  muscles  which  can  be  effected  with  case  for  a  length 
of  time,  then  we  can  look  at  the  object  steadily  and  ci:)ni- 
fortably. 

Therefore  the  proper  position  of  the  book  in  reading  does 
not  depend  on  chance,  but  is  a  physiological  necessity.  If  it 
is  constantly  disregarded  the  eyes  become  fatigued  and  a  con- 
dition of  asthenopia  may  intervene.  This  is  the  reason  why 
it  is  so  tiring  to  look  at  those  pictures  in  a  gallery  which  are 


156  MYOI'IA. 

hung-  high  on  the  wall,  while  the  same  number  of  pictures 
can  be  examined  without  fatigue  if  placed  on  easels  below  the 
level  of  the  eyes.  Likewise  it  is  hurtful  to  the  eyes  to  read 
while  lying  down,  and  if  this  pernicious  habit  is  persisted  in 
will  sooner  or  later  ])nuluce  a  painful  and  weak  condition  of 
the  eyes. 

Conse(|uentIy,  if  we  want  to  look  for  any  length  of  tinu- 
at  any  plane  surface,  as  for  instance,  the  page  of  a  ])ook.  it  is 
necessary  to  place  it  and  hold  it  in  such  a  position  as  to  form 
an  angle  of  about  45°  with  the  horizon,  and  then  direct  the 
axis  of  vision  of  our  eyes  downward  at  an  equal  ang-le  of  45°, 
so  that  a  right  ang-le  will  be  formed  by  their  intersection,  or 
in  other  words,  that  the  visual  axis  may  be  perpendicular  to 
the  surface  of  the  book.  This  is  the  ideal  position  for  the  book 
and  eyes  in  reading,  and  if  the  reader  will  look  around  him 
he  will  see  how  many  persons  disregard  these  plainly  proven 
propositions.  For  writing,  the  same  inclination  for  the  paper 
would  be  equally  advantageous,  but  for  obvious  reasons  this 
would  scarcely  be  practicable,  and  for  this  purpose  a  less  angle 
is  recommended,  usually  about  20°.  It  is  possible  to  have  a 
desk  so  constructed  that  the  inclination  of  its  top  might  be 
changed  by  a  simple  mechanism. 

It  is  obvious  that  a  flat-top  desk  not  only  prevents  the 
direction  of  the  visual  axis  at  that  angle  most  favorable  to  the 
natural  and  easy  movement  of  the  eye-ball,  but  also  encourages 
a  stooping  position  with  its  attendant  evils  of  close  sight  and 
gravitation  of  blood  to  the  eyes. 

The  influence  of  school  life  upon  the  figure  of  the  child 
and  in  the  causation  of  curvature  of  the  spine,  as  well  as  the 
disastrous  effects  that  crooked  and  stooping  positions  at  school 
may  have  upon  the  heart  and  lungs  and  abdominal  organs, 
are  important  matters  for  serious  consideration,  but  it  is  not  in 
place  to  discuss  them  here,  as  they  are  beyond  the  scope  of  this 
work. 

BLACKBOARDS  AND   MAPS. 

Attention  should  also  be  given  to  the  distance  and  location 
of  blackboards,  as  an  important  factor  in  the  hygiene  of  school 
vision.  Tliey  should  not  be  placed  so  far  away  from  any 
scholar  as  to  necessitate  a  strain  in  order  to  see  the  marks 


MYOPIA.  ^^' 


upon  their  surfaces,  but  those  pupils  who  have  dekctive  vision 
should  be  LHven  front  seats  near  the  board.  No  blackboard 
should  ever  be  placed  between  two  windows,  as  the  scholar 
could  not  see  the  writing  upon  it  without  subjecting  his  eyes 
to  the  irritating  glare  of  light  which  enters  the  eye  from  an  im- 
proper direction,  while  the  board  remains  in  shadow;  but  the 
light  should  be  so  arranged  as  to  illuminate  the  board  without 
causing  its  rays  to  be  reflected  in  such  a  manner  as  to  obscure 
the  characters  that  are  inscribed  thereon. 

Some  authorities  have  recommended,  as  a  desirable  sub- 
stitute, white  surfaces  with  black  crayons,  on  the  presumption 
that  black  marks  on  a  white  background  can  be  seen  at  a 
greater  distance.  But  on  the  other  hand,  the  reflection  from 
a  large  extent  of  white  surface  is  more  apt  to  be  annoying  and 
irritating  to  the  eye  than  is  the  same  amount  of  black  surface, 
and  therefore  we  think  the  old  form  of  blackboard  and  white 
crayon  cannot  be  improved  upon.  For  similar  reasons,  the 
writer  has  been  using  in  his  offtce  for  determining  the  acute- 
ness  of  vision  and  measuring  the  refraction,  a  black  card  with 
white  block  letters  upon  it,  and  finds  it  very  satisfactory. 

THE  TYPE  OF  TEXT-BOOKS. 

The  size  and  form  of  the  type  used  in  school  books  are  of 
great  importance  from  a  hygienic  standpoint.  All  authorities 
agree  that  the  Latin  letters  are  the  best  for  all  kinds  of  reading. 
The  crooked  zig-zag  lines  of  the  German  letters  are  by  com- 
mon consent  considered  very  trying  to  the  eyes,  and  hence 
that  form  of  letters  should  never  be  employed  in  text-books. 
It  is  altogether  likely  that  this  type,  in  connection  with  the 
studious  habits  of  the  German  nation,  are  responsible  for  the 
larger  percentage  of  myopia  in  that  country,  in  speaking  of 
which  an  author  says,  "it  is  certain  that  if  Germany  would 
absolve  itself  from  nationalism  sufficiently  to  declare  an  eman- 
cipation from  its  miserable  type,  there  would  be  less  myopia 
among  its  people." 

The  normal  acuity  of  vision  is  based  upon  the  ability  to 
distinguish  letters  which  subtend  an  angle  of  five  minutes,  but 
it  would  be  very  unreasonable  to  expect  the  eyes  to  keep  at  a 
task  for  any  great  length  of  time  which  called  forth  their 


158  MYOPIA. 

Utmost  endeavor.  This  will  become  evident  to  any  one  who 
compares  the  strain  and  effort  to  read  small  (diamond)  type, 
with  the  ease  and  comfort  with  which  a  larger  type  (long 
primer)  is  read,  and  the  latter  (the  size  in  which  this  article  is 
set)  is  the  smallest  which  should  be  allowed  in  school  books, 
or  for  that  matter  in  any  book  intended  for  general  reading. 

The  distance  between  the  lines  has  much  to  do  with  the 
legibility  of  the  page  and  with  the  ease  with  which  it  is  read. 
When  the  lines  are  crow^ded  as  closely  together  as  the  type  will 
permit,  the  page  has  a  dark  and  unattractive  appearance,  and 
the  labor  of  reading  is  relatively  increased,  as  is  evident  to  any 
one  who  will  compare  a  closely  set  page  of  reading  matter  with 
one  that  is  liberally  leaded.  The  fact  is,  a  proper  spacing  be- 
tween the  lines  is  really  of  more  importance  than  the  size  and 
height  of  the  letters,  and  the  weight  of  opinion  is  that  this  space 
should  not  be  less  than  two  and  a  half  millimeters,  or  one- 
tenth  of  an  inch.  The  printing  should  be  well  done,  so  that 
the  letters  show  up  clear  and  distinct.  If  a  large  edition  of  a 
book  is  issued,  those  first  run  off  are  clearest,  and  later  on  the 
print  begins  to  appear  somewhat  blurred  and  defective.  As 
soon  as  this  is  noticeable  the  type  (or  electrotype  which  is  gen- 
erally used)  should  be  rejected  and  new  metal  demanded. 

The  paper  should  be  of  good  quality,  as  otherwise  the 
beneficial  effect  of  large  type  properly  spaced  would  be  neu- 
tralized. It  should  be  reasonably  thick  and  opaque,  so  that 
the  impression  of  the  type  on  the  opposite  side  should  not 
show  through.  The  surface  of  the  paper  should  be  dulled,  so 
that  there  may  be  no  unpleasant  reflection  from  it,  and  of  a 
cream  tint. 

PROPER  PENMANSHIP. 

We  do  not  propose  to  go  very  deeply  into  the  considera- 
tion of  the  question  of  vertical  or  slanting  handwriting,  but 
some  mention  of  it  is  due  on  account  of  the  agitation  of  the 
subject  at  the  present  day.  There  appears  to  be  a  growing 
sentiment  in  favor  of  the  erect  system,  because  the  slanting- 
form  seems  to  favor  an  unnatural  position  of  the  body  and  of 
the  paper,  and  thus  tend  to  the  development  of  myopia.  But 
if  the  desk  and  seat  are  of  the  proper  proportions,  and  the  pupil 
rightly  seated  with  the  paper  in  a  central  position  in  front  of 


159 

is  im- 


him,  the  question  of  the  selection  of  the  kind  of  script 
material  from  tlie  standpoint  of  the  hygiene  of  vision,  which  is 
the  only  point  in  whicii  we,  as  opticians,  are  interested. 

HOURS  OF  STUDY. 

Young  children  should  not  be  expected  to  use  their  eyes 
more  than  a  few  hours  each  day;  all  their  work  should  be  done 
in  the  school  room,  and  when  they  leave  it  their  minds  and 
bodies  should  be  free  from  any  set  tasks.  As  the  child  in- 
creases in  years  and  advances  into  the  higher  grades,  some 
amount  of  study  is  necessary  out  of  school,  and  it  seems  pos- 
sible that  more  harm  may  be  done  to  the  eyes  by  indiscretion 
in  the  home  work  than  in  school  hours.  Children  are  usually 
under  less  discipline  at  home  than  at  school;  they  are  often 
allowed  to  read  what,  when  and  how  they  please;  no  provision 
is  made  for  proper  desks,  seats  or  light;  the  child  assumes 
various  positions  and  often  reads  while  reclining,  with  light 
that  is  perhaps  insufficient  or  coming  from  a  wrong  direction. 
As  a  rule,  children  are  sent  to  school  too  early  in  life ;  in 
many  instances  because  the  mother  wishes  to  be  rid  of  the 
annoyance  of  the  child  for  a  few  hours  each  day,  and  because 
the  law  allows  it.  Seven  years  of  age  is  young  enough  for  a 
child  to  enter  school,  although  six  years  is  the  legal  age;  but 
really  such  an  important  matter  cannot  be  regulated  by  statute, 
but  should  depend  on  the  physical  condition  of  each  individual 
child. 

PREVENTIVE    MEASURES. 

In  the  prevention  of  the  development  of  myopia  in  chil- 
dren, the  importance  of  giving  to  the  child  for  his  playthings 
objects  of  considerable  size  becomes  evident.  Small  ones, 
books  with  fine  print  and  games  with  minute  figures,  all  im- 
pose a  tax  upon  the  accommodation  and  should  be  avoided. 
On  the  other  hand,  out-door  plays  should  be  encouraged,  be- 
cause they  do  not  require  any  close  vision,  or  at  least  all  play 
objects  should  be  sufficiently  large  not  to  require  any  effort  of 
accommodation.  After  the  child  enters  school  he  should  not 
be  required  to  keep  his  eyes  uninterruptedly  upon  the  book, 
as  some  teachers  with  mistaken  zeal  insist  upon,  under  penalty 
of  receiving  a  bad  mark  for  misconduct,  but  he  should  rather 


IGO  MY(,)PIA. 

be  encouraged  to  rest  liis  eyes  and  relieve  their  fatigue  by 
looking-  up  from  his  books  and  glancing  around  at  more  dis- 
tant objects. 

Frequent  interruption  of  any  kind  of  confining  work  is 
essential  to  symmetrical  development  and  the  maintenance 
of  a  healthy  condition  of  the  body,  and  this  is  especially  true 
of  the  young.  If  one  attempts  to  hold  up  an  object  at  arm's 
length,  and  thus  imposes  a  continued  effort  upon  these 
muscles,  a  feeling  of  strain  and  exhaustion  soon  becomes  ap- 
parent, and  the  act  must  be  quickly  discontinued;  and  yet  the 
muscles  of  the  eyes  are  often  forced  to  do  similar  work:  is  it 
any  wonder  then  that  myopia  results? 

Myopia  is  seldom  congenital,  although  it  may  be  heredi- 
tary and  appear  soon  after  birth.  It  rarely  develops,  however, 
before  the  eighth  year  of  life,  more  often  the  tenth,  and  reaches 
its  maximum  about  the  ag-e  of  twenty.  Where  an  inherited 
predisposition  to  myopia  exists,  the  child  should  be  kept  out 
of  the  school  room  as  long  as  possible ;  perhaps  until  he  is  ten 
or  eleven  years  old.  In  the  meantime,  and  in  fact  all  through 
life,  open-air  sports  should  be  encouraged,  with  gymnastic 
exercises  for  the  development  of  the  body  and  perhaps  an  in- 
termixture of  properly  assigned  manual  labor. 

The  fact  should  be  impressed  upon  the  minds  of  parents 
and  edticators  that  it  is  better  to  devote  the  years  of  youth  to 
laying  the  foundation  of  a  healthy  constitution  and  strong  eyes 
than  to  encourage  forced  intellectual  advancement  at  the  ex- 
pense of  feeble  health  and  impaired  vision.  The  moral  of  this 
advice  is  emphasized  by  the  country  boy,  raised  upon  the  farm 
and  receiving  but  few  educational  advantages,  who  so  often 
outstrips  his  city  cousin,  whose  life  from  four  years  of  age  has 
been  spent  in  kindergartens  and  graded  schools. 

For  those  predisposed  to  myopia,  mental  education 
should  be  always  subject  to  the  physical  condition,  and  earnest, 
systematic  study  should  not  be  commenced  until  the  sixteenth 
year,  when  the  body  is  stronger  and  the  coats  of  the  eye  firmer 
and  better  able  to  resist  the  encroachments  of  myopia.  Even 
then  it  w^ould  be  better  if  the  child  could  be  taught  privately, 
instead  of  being  placed  in  the  general  class  and  expected  to 
keep  pace  with  his  normal-sighted  companions. 


MYOPIA.  Ifil 

In  order  to  prevent  the  onset  of  myopia,  or  its  increase, 
the  stooping  position  and  a  close  approximation  of  the  book, 
which  taxes  both  accommodation  and  convergence,  must  be 
avoided;  the  patient  should  be  instructed  never  to  read  in  a 
moving  car  or  carriage,  where  the  continual  jarring  requires  a 
constant  change  in  the  accommodation;  not  to  continue  close 
vision  too  long  at  a  time  without  suitable  periods  of  inter- 
mission: to  maintain  a  reading,  writing  or  working  distance  of 
at  least  twelve  inches,  and  more  if  {x^ssible;  tO'  select  books  and 
newspapers  printed  in  clear,  large  type;  to  avoid  fine  sewing 
and  tedious  fancy  work;  to  write  a  large  hand  (as  myopes  are 
especially  prone  to  small  writing) ;  to  see  that  daylight  is  suf- 
ficient in  quantity  and  coming  from  the  proper  direction;  not 
to  use  the  eyes  by  artificial  light,  or  as  little  as  possible;  and  if 
symptoms  of  irritation  become  manifest,  or  there  is  a  marked 
increase  in  the  myopia,  to  give  the  eyes  complete  rest. 

TESTS   FOR  MYOPIA. 

In  myopia  the  distant  vision  is  impaired,  while  the  close 
vision  remains  fairly  good,  and  therefore  if  a  person  is  unable 
to  make  out  the  large  letters  on  the  test  card,  hanging  twenty 
feet  distant,  but  can  easily  read  the  small  print  six  or  seven 
inches  away,  it  is  fair  to  presume  he  is  myopic.  This  is  a 
rough  test,  but  it  is  one  of  value,  and  can  be  made  at  any  time 
and  under  any  circumstances  and  without  any  outfit.  An 
ordinary  newspaper  can  be  made  to  suffice,  the  letters  of  the 
title  line  forming  the  distance  test  and  the  small  type  the  near 
test.  Of  course,  if  with  the  impairment  of  distant  sight  near 
vision  is  also  defective  or  imposible,  there  is  something  more 
than  myopia;  perhaps  amblyopia,  or  some  diseased  condition. 

The  differential  diagnosis  between  myopia  (which  is  cor- 
rectible  with  glasses)  and  an  organic  disease  (which  is  beyond 
the  reach  of  optical  help)  can  be  quickly  made  by  means  of  the 
pin-hole  test,  which  has  been  described  and  illustrated  on 
pages  in  The  Optician's  Manual.  Tlie  trial  case  contains 
one  or  two  of  these  pin-hole  disks,  made  of  hard  rubber  and 
mounted  in  a  metal  ring  with  handle;  but  in  the  absence  of  a 
test  case,  a  card  or  a  stifT  piece  of  paper  can  be  punctured  with 
a  pin;  an  equally  efficacious  pin-hole  test  is  at  hand,  and  one 


'••■-  MYOPIA. 

that  can  he  iiK'uk'  and  used  in  any  lonely  cahin  in  the  hack- 
woods. 

The  principal  tests  for  niyoi)ia  are: 

1.  Trial  case  and  test  types. 

2.  Ophthalmoscope. 

3.  Rctinoscopc. 

4.  Refractometer,  optometer,  prisoptometer. 

5.  Scheiner's  method. 

6.  Chromatic  test. 

TEST    WITH   TRIAL   LENSES. 

The  patient  is  seated  facing  the  test  card  of  Snellen,  which 
is  well  illuminated  and  hanging  twenty  feet  away.  The  trial 
frame  is  placed  on  his  face  and  carefully  adjusted  for  height 
of  nose  and  pupillary  distance.  Both  eyes  should  be  kept 
open,  but  only  one  eye  should  be  tested  at  a  time,  the  other 
being  excluded  from  vision  by  a  solid  rubber  disk  being  placed 
in  the  trial  frame  over  it. 

The  left  eye  being  thus  covered,  the  patient  is  asked  to 
name  the  letters  on  the  lowest  line  which  is  legible  to  him. 
If  he  reads  the  No.  20  line,  that  is  if  his  visual  acuteness  is  f^, 
the  eye  is  presumably  emmetropic,  although  latent  hyperme- 
tropia  may  be  present.  If  he  reads  the  line  hesitatingly  and 
makes  some  mistakes  in  naming  the  letters,  there  is  prob- 
ably some  astigmatic  element  in  the  case.  But  either  of  the 
above  conditions  precludes  the  existence  of  myopia,  which 
cannot  be  present  if  the  vision  is  wholly  or  even  partly  fi}, 
because  this  defect  markedly  impairs  the  acuteness  of  vision. 

If,  however,  the  patient  cannot  distinguish  any  letters  on 
the  Xo.  20  line,  and  perhaps  cannot  even  read  the  30  or  40 
lines,  we  may  infer  the  possibility  of  myopia;  but  first  in  order 
to  prevent  error,  convex  glasses  must  be  tried  in  order  to 
detect  any  hypermetropia.  If  they  are  immediately  and  posi- 
tively rejected,  it  is  then  proper  to  begin  to  suspect  myopia, 
and  we  ask  the  patient  to  take  the  line  near  type  (which  a 
myope  is  easily  able  to  read)  and  move  it  away  from  him  to 
the  greatest  possible  distance  from  the  eye  at  which  it  can 
still  be  seen  distinctly.    The  distance  from  the  eye  to  the  type 


M^'()IM.\.  103 

is  then  carefully  measured,  which,  when  converted  into  diop- 
trics, will  represent  (at  least  approximately)  the  degree  of 
myopia,  and  the  corresponding  concave  lens  will  be  the  proper 
correction.  This  glass  is  placed  in  the  trial  frame  in  front  of 
the  eye  and  the  distant  vision  is  again  tested.  The  strength 
of  the  lens  is  diminished  or  increased,  if  necessary,  until  the 
maximum  acuity  of  vision  is  obtained,  always  reineiuhering 
to  give  the  preference  to  the  weakest  glass. 

The  other  e}C  is  then  similarly  tested,  and  when  both 
eyes  are  corrected  an  effort  should  be  made  to  reduce  the 
strength  of  the  glasses  by  placing  weak  convex  lenses  in 
front  of  them.  If  any  glass  above  +  .50  D.  is  thus  accepted, 
the  examiner's  suspicions  should  be  aroused  as  to  the  possi- 
ble existence  of  spasm  of  accommodation.  Otherwise  the 
lenses  may  be  considered  as  correct. 

A  recent  book  says:  "Take  in  your  hand  a  +  .50  D.  S. 
and  a  —  -50  D.  S.,  trying  first  one  and  then  the  other  before 
the  eye  you  are  testing.  Whichever  lens  gives  the  best 
vision,  after  a  careful  trial,  will  be  an  indication  of  what  kind 
of  lenses  (convex  or  concave)  the  patient  is  going  to  need." 
Now  we  are  compelled  to  take  issue  with  the  author  of 
this  work,  as  we  cannot  consider  such  a  method  of  testing  as 
proper.  It  is  a  well-known  fact  that  a  weak  concave  lens  will 
be  accepted  for  distance  by  almost  any  eye,  even  by  emme- 
tropic and  hypermetropic  eyes,  and  in  slight  degrees  of  the 
latter  defect  will  be  preferred  to  weak  convex.  Therefore 
when  weak  plus  and  minus  lenses  are  tried  alternately,  the 
patient  will  most  likely  select  the  concave,  or  else  he  will  be 
confused  and  will  be  unable  to  decide  between  them.  Tlie 
writer  feels  that  he  can  make  the  positive  statement  that  in 
such  a  method  of  testing  the  convex  lens  would  never  be 
chosen ;  this  makes  the  test  entirely  one-sided  and  robs  it  of 
its  value. 

The  advice  given  on  these  pages  has  always  been  to  com- 
mence the  test  with  convex  lenses,  and  if  they  are  accepted 
at  all,  not  to  confuse  the  patient  or  run  the  risk  of  error  by 
trying  concaves,  and  this  advice  is  especially  applicable  in  cases 
where  the  vision  is  fSy  or  nearly  so.  Where  the  vision  is 
markedlv  below  normal,  the  rule  still  holds  good  to  begin  the 


lG-4  MVoriA. 

examination  with  convex  lenses,  and  only  in  case  of  their  posi- 
tive rejection  is  it  proper  to  try  concaves. 

After  these  preliminaries,  suppose  —  .50  D.  lens  quickly 
and  unmistakably  improves  vision  on  the  test  card,  it  is  prob- 
able the  case  is  one  of  myopia  and  needs  concave  lenses.  Tlien 
the  —  .50  D.  is  removed  and  a  —  .75  D.  is  substituted  for  it. 
with  a  still  g-reatcr  improvement  in  vision,  which  possibly  may 
now  reach  the  normal  standard  of  f  ^ ,  in  which  case  this  lens 
would  be  the  measure  of  the  defect.  If  not,  a  —  i  D.  is 
next  tried,  and  as  long  as  a  further  improvement  in  vision  is 
obtained,  the  lenses  are  gradually  increased  in  strength  a  .25 
D.  at  a  time  until  the  best  vision  is  secured  that  it  is  possible 


This  diagram  shows  the  path  of  the  rays  and  the  position  of 
the  image.  The  rays  issue  from  the  myopic  eye  convergently 
and  focus  ten  inches  in  front  of  it;  they  then  cross  and  enter 
the  emmetropic  eye  and  are  united  upon  its  retina. 

to  get  with  concave  spherical  glasses,  always  remembering 
that  the  w^eakest  glass  is  the  one  to  be  preferred. 

This  lens  is  then  placed  in  the  back  groove  of  the  trial 
frame  and  the  rubber  disk  slipped  in  front  of  it,  and  a  similar 
test  made  of  the  other  eye.  After  the  second  eye  has  been 
carefully  measured,  the  rubber  disk  is  removed  from  before 
the  first  eye  and  the  patient  can  see  with  his  both  eyes  to- 
gether, each  properly  corrected  as  far  as  can  be  with  spherical 
lenses. 

The  frequent  change  of  lenses  in  the  trial  frame  is  more 
or  less  confusing  to  the  patient,  and  should  be  avoided  as 
much  as  possible.  Hence  in  high  degrees  of  defect,  instead 
of  increasing  .25  D.  at  a  time,  it  is  better  to  jump  .50  D.,  or 
even  i  D.,  until  something  near  the  normal  acuteness  of  vision 
is  reached,  and  then  proceed  more  cautiously  and  with  shorter 
steps.     When  lenses  are  found  that  afford  pretty  fair  vision. 


MVOPIA.  1G5 

instead  of  removing  the  lens  and  replacing-  it  with  another, 
its  strength  may  be  increased  or  decreased  by  holding 
before  it  alternately  a  —  .25  D.  and  a  +  .25  D.  If  with 
the  convex  lens  vision  remains  as  good,  then  the  concave 
lens  in  the  frame  is  stronger  than  is  necessary,  and  should 
be  reduced  a  quarter  of  a  dioptric.  If  on  the  other  hand  the 
—  .25  D.  produces  a  marked  improvement  in  vision,  then  the 
lens  in  the  frame  is  not  quite  strong  enough,  and  should  be 
replaced  by  one  a  quarter  of  a  dioptric  stronger. 

NORMAL    VISIOX    NOT    ALWAYS    POSSIBLE    IN    HIGH    MYOPIA. 

If  with  the  lenses  found  according  to  the  above  methods 
the  patient,  at  twenty  feet,  can  read  the  No.  20  line  clearly 
and  distinctly,  it  is  right  to  assume  that  the  full  defect  has 
been  measured  and  the  proper  correcting  lenses  found.  Even 
if  the  vision  is  less  than  |^,  with  these  glasses  it  does  not 
prove  they  are  incorrect ;  it  simply  shows  this  is  the  best  vision 
attainable  with  concave  spherical  lenses. 

In  high  degrees  of  myopia  it  is  an  unfortunate  fact  that 
vision  cannot  be  raised  to  normal  by  any  glass,  and  this  may 
perhaps  be  comforting  knowledge  to  some  conscientious 
opticians  who  have  vainly  endeavored  to  tind  some  glass  that 
would  aflford  a  vision  of-j^.  There  are  two  reasons  for  this 
— the  impaired  sensibility  of  the  retina  and  the  diminishing 
effect  of  concave  lenses.  Either  one  of  these  would  be  suf- 
ficient to  account  for  the  lessened  vision,  while  the  two  to- 
gether only  serve  to  make  it  more  pronounced. 

In  extreme  cases  of  myopia  there  is  great  bulging  of  the 
fundus  and  stretching  of  all  the  coats  of  the  eye,  in  which 
process  the  retina  is  the  membrane  that  suffers  the  most,  its 
layer  of  rods  and  cones  being  separated  and  fewer  of  them 
being  impressed  by  the  image  formed,  and  therefore  the 
degree  of  vision  would  be  lessened.  The  function  of  a  con- 
cave lens  is  to  minify,  and  the  diminution  of  an  image  by 
strong  minus  lenses  is  very  marked,  and  hence  such  a  glass, 
by  reducing  the  image  formed,  would  tend  to  impair  the  acute- 
ness  of  vision  very  perceptibly.  When  these  two  causes  act 
together  and  an  image  s;iialler  than  normal  is  received  by 
a  less  number  of  rods  and  cones  than  natural,  the  wonder 


](!(')  MYOPIA. 

rcalh-  is  that  the  xisioii  is  as  suscej)til)lc  of  as  iiuich  iniprove- 
inent  as  it  is. 

TEST    WITH    OrilTII.M.MOSCOrE. 

In  emnictropia  parallel  rays  are  brought  to  a  focus  ex- 
actly on  the  retina  and,  therefore  inasmuch  as  the  retina  is 
located  precisely  at  the  principal  focus,  the  divergent  rays 
proceeding  from  it  (after  being  acted  on  by  the  refracting 
media  of  the  eye)  would  emerge  from  the  cornea  parallel. 

In  myopia,  on  the  other  hand,  the  retina  is  placed  beyond 
the  principal  focus  and  parallel  rays  unite  and  cross  over  be- 
fore reaching  it.  Under  such  conditions  the  rays  proceeding 
from  the  retina  would  emerge  from  the  eye  convergent  and 
would  meet  at  this  far  point. 

When  looking  into  an  emmetropic  eye  with  an  ophthal- 
moscope, the  observer  must  approach  within  two  or  three 
inches  in  order  to  see  the  details  of  the  fundus  clearly.  In 
myopia,  on  the  contrary,  nothing  can  be  clearly  seen  at  such 
a  close  distance  with  the  naked  eye,  but  on  withdrawing  the 
instrument  from  fifteen  to  twenty  inches,  the  optic  disk  and 
blood-vessels  will  gradually  come  more  or  less  clearly  into 
view. 

In  a  case  of  myopia  of  4  D.  the  rays  reflected  from  the 
retina  would  converge  and  meet  at  a  distance  of  ten  inches 
from  the  eye  and  form  there  an  inverted  image,  which  can 
be  clearly  seen  by  the  optician,  at  his  ordinary  distance  for 
small  objects  (say  from  ten  to  twelve  inches),  by  calling  into 
action  his  accommodation  and  adjusting  his  eye  for  that  par- 
ticular spot  at  which  the  aerial  image  is  formed.  In  this  case, 
where  the  image  is  at  ten  inches  and  the  observer's  eye  ten 
inches  from  that,  it  will  be  found  that  a  distance  of  twenty 
inches  will  be  the  proper  one  to  assume.  The  precaution 
must  be  taken  not  to  approach  the  image  too  close — that  is, 
the  optician  must  always  keep  beyond  his  own  near  point,  else 
his  accommodation  will  not  suf^ce  to  afTord  him  a  distinct 
view. 

That  this  image  is  inverted  is  proven  by  the  fact  that 
when  the  observer  moves  his  head  slightly  from  side  to  side 
the  image  moves  in  the  opposite  direction,  hence  a  contrary 
movement  of  the  image,  when   the  ophthalmoscope   is   held 


MVdPlA.  167 

some  little  distance  away,  is  one  of  the  diagnostic  tests  for 
myopia. 

Direct  Method. — Inasmuch  as  the  emergent  rays  from  a 
myopic  eye  are  convergent,  it  is  evident  that  such  converg- 
ing- rays  cannot  be  focused  upon  the  retina  of  an  emmetropic 
observer,  and  hence  an  erect  image  of  the  myopic  fimdus  is 
impossible  without  the  aid  of  a  concave  lens  to  lessen  their 
convergence. 

The  rule  then  in  simple  m\opia  is  to  ascertain  the  weakest 
concave  lens  that  will  render  the  fundus  clear  and  distinct  as 
being  the  approximate  measure  of  the  defect.  After  a  few 
trials  it  is  easy  to  decide  which  concave  lens,  rotated  into  the 
sight  hole  of  the  instrument,  will  afford  the  clearest  image. 

The  accuracy  of  this  method  (the  direct  method  of  the 
ophthalmoscope)  presumes  the  corneae  of  observer  and  patient 
to  be  in  actual  contact,  but  as  that  is  impossible,  the  distance 
between  them  should  be  added  to  the  focal  length  of  the  lens 
found  as  above. 

For  instance,  by  referring  to  the  illustration  (page  164) 
the  rays  are  seen  to  cross  ten  inches  from  the  myopic  eye.  Sup- 
pose the  observer  placed  his  eye  one  inch  in  front  of  it,  then  the 
position  of  the  focus  is  nine  inches  back  of  his  cornea,  and 
therefore  a  —  4.50  D.  lens  in  the  aperture  of  the  ophthalmo- 
scope would  render  the  rays  parallel  and  allow  thetn  to  be 
focused  on  his  retina  without  any  efifort  of  accommodation. 
But  as  is  evident  from  the  illustration,  this  —  4.50  I),  lens 
is  more  than  the  full  measure  of  the  defect:  but  by  adding 
the  distance  between  the  eyes  of  patient  and  observer  to  the 
focal  distance  of  the  lens  found  as  above,  the  result  will  be  the 
exact  measure  of  the  myopia  present  in  patient's  eye  (i  inch 
added  to  9  inches  =  10  inches  focal  distance,  or  a  refractiv* 
power  of  —  4  D.;  it  being  understood  that  an  increase  of  dis- 
tance represents  less  optical  defect). 

Tlie  rule  then  is  that  the  weakest  concave  lens  that  renders 
the  details  of  the  fundus  clear  and  distinct  will  be  the  extent  of 
the  myopia.  Suppose  when  the  optician  looks  into  an  eye 
through  the  aperture  of  his  ophthalmoscoi>e  everything  about 
the  fundus  appears  blurred  and  indistinct;  a  convex  lens  is 
then  rotated  into  the  sight  hole,  with  the  etTect  of  making  it 


IGS  MYOPIA. 

worse;  now  the  weakest  concave  lens  is  tried,  and  at  once  the 
fundus  begins  to  look  clearer;  then  another  and  another  i^s 
used,  until  finally  all  the  details  of  the  eye-ground  arc  brought 
out  distinctly,  and  this  lens  will  approximately  represent  the 
degree  of  the  myopia.  It  should  always  be  remembered  that 
preference  is  to  be  given  to  weakest  concave  lens  that  renders 
the  fundus  distinct. 

SKLF-RELAXATIOK   OF  THE  ACCOMMODATION. 

In  attempting  to  determine  the  amount  of  myopia  by  the 
direct  method  of  the  ophthalmoscope,  the  accommodation  of 
both  observer  and  patient  is  supposed  to  be  at  rest,  and  upon 
this  fact  rests  the  accuracy  of  this  method.  Otherwise  a  con- 
dition of  false  myopia  is  temporarily  produced  by  the  invol- 
untary use  of  the  ciliary  muscle  in  either  optician  or  patient, 
which  would  require  a  concave  lens  to  enable  the  details  of  the 
fundus  to  be  clearly  seen.  This  is  an  error  into  which  many 
beginners  fall,  thinking  they  have  a  case  of  myopia  to  deal 
with,  because  a  concave  lens  brings  out  the  blood-vessels  and 
optic  disk  more  shai"ply,  w^iereas  it  may  be  emmetropic  or  even 
hypermetropia  metamorphosed  by  the  accommodation. 

The  patient's  accommodation  is  encouraged  to  relax  by 
the  dark  room,  and  by  requesting  him  to  direct  his  eyes  to  a 
distance,  without  however  attempting  to  fix  the  vision  on  any 
particular  object.  But  it  is  not  so  easy  for  the  optician  to 
relax  his  power  of  accommodation,  because  he  is  inclined, 
naturally,  to  look  at  the  fundus  of  the  patient's  eye  as  at  a  near 
point;  whereas  it  should  be  viewed  as  if  at  infinite  distance  with 
a  relaxed  ciliary  muscle. 

The  faculty  of  placing  the  ciliar}-  muscle  at  rest  is  one 
that  can  be  acquired  by  the  optician,  in  the  practice  of  which 
the  following  exercises  have  been  recommended  as  facilitating' 
that  end. 

1.  The  optician  directs  his  eyes  toward  the  ceiling,  and 
while  in  that  position  holds  above  them  a  sheet  of  white  paper 
upon  which  there  is  a  black  ink  spot.  When  he  notices  that 
the  spot  appears  double,  the  paper  and  the  eyes  are  to  be  slowly 
lowered  and  the  endeavor  made  to  keep  the  gaze  directed  into 
distance  and  the  accommodation  at  rest,  in  which  case  the  dot 


MYOPIA.  169 

will  continue  to  appear  double,  even  when  it  is  below  the  level 
of  the  eyes.  It  is  comparatively  easy  to  get  the  double  vision 
when  the  spot  is  high  up  over  the  eyes,  but  the  difficulty  in- 
creases as  the  object  is  lowered  to  the  level  of  or  below  the 
eyes. 

2.  The  finger  or  a  pencil  should  be  held  ten  or  twelve 
inches  in  front  of  the,  face,  and  as  long  as  the  gaze  is  kept  at 
a  distance  and  the  accommodation  remains  quiescent,  the  ob- 
ject will  appear  double. 

3.  While  reading  a  book  or  card  of  fine  print,  held  quite 
close  to  the  eyes,  the  optician  attempts  to  look  through  and 
beyond  the  book  or  card,  as  it  were,  when  the  lack  of  accom- 
modation will  cause  the  letters  to  run  together  and  become 
blurred.  At  the  same  time  the  convergence  can  be  felt  to 
lessen  and  the  eyes  to  assume  a  parallel  condition. 

By  a  frequent  repetition  of  these  exercises,  the  optician  can 
learn  to  bring  an  object  close  to  the  eyes  without  bringing 
into  play  his  accommodation  or  convergence,  and  with  the 
accommodation  thus  under  his  control,  he  is  in  a  position  tcj 
obtain  the  most  accurate  results  in  the  estimation  of  the 
amount  of  myopia  by  the  direct  method  of  the  ophthalmo- 
scope, which,  however,  should  always  be  verified  by  the  sul)- 
jective  examination. 

1X1)1  KIXT   METHOD    OF   OPHTHALMOSCOPE. 

By  the  indirect  method  the  eye  is  viewed  at  a  distance  of 
twelve  to  fifteen  inches  (usual  reading  distance)  through  a 
strong  convex  lens  held  at  its  focal  distance  from  the  patient's 
eye.  An  inverted  image  of  the  optic  disk  and  blood-vessels 
is  seen,  which  is  sharper  but  smaller  than  by  the  direct  method. 
In  myopia  this  inverted  image  of  the  disk  is  smaller  than  in 
enunetropia,  but  increases  in  size  as  the  strong  convex  lens  is 
withdrawn  from  the  patient's  eye.  While  the  indirect  method 
gives  a  larger  field,  and  thus  favors  a  more  rapid  examination 
of  the  whole  fundus,  yet  for  determining  the  refraction  of  an 
eye  the  direct  method  is  much  to  be  preferred,  and  besides  it  is 
not  so  difficult  for  the  beginner  to  learn. 


170 


TKST    WITH     KKTlXOSCOrE. 

The  essentials  for  the  rctinoscope  test,  with  full  instruc- 
tions as  to  how  it  should  be  conducted,  were  described  in  the 
chapter  on  "Hypennetropia."  When  the  shadow  in  the  pupil 
moves  in  an  opposite  direction  to  the  light  on  the  face,  the  eye 
is  known  to  be  myopic  (the  plane  mirror  being-  used),  and  con- 
cave spherical  lenses  are  placed  in  the  trial  frame  until  the 
weakest  glass  is  found  which  reverses  the  movement  of  shadow 
and  makes  it  travel  in  the  same  direction  as  the  light  on  the 
face.  This  is  the  correcting  lens  at  the  distance  at  which  the 
examination  is  conducted,  to  which  must  l)e  added  the  lens 
representing  that  distance  ( —  i  D.). 

Suppose,  for  example,  the  far  point  of  the  myopic  eye  is 
at  ten  inches,  and  if  the  eye  was  examined  at  a  (Hstance  of 
twenty  feet  a  concave  lens  of  4  D.  would  render  the  rays  of 
light  parallel  and  stop  all  retinal  reflex.  But  as  the  examina- 
tion is  conducted  at  a  distance  of  only  one  metre  or  forty 
inches,  a  lens  of  —  3D.  will  be  sufficient  to  halt  the  reflex; 
and,  therefore,  in  estimating  the  total  amount  of  myopia,,  i  D. 
must  be  added. 

TESTS  WITH  INSTRUMENTS. 

Rcfractomctcr. — As  the  patient  loo'ks  through  this  instru- 
ment at  the  test  card,  hanging  fifteen  or  twenty  feet  away,  any 
desired  number  of  convex  or  concave  lens  can  be  placed  before 
his  eye  by  simply  rotating  a  wheel  on  the  side  of  the  tube, 
which  is  marked  in  dioptrics  and  fractions  thereof,  and  num- 
bered in  red  and  white  to  distinguish  between  convex  and  con- 
cave. The  revolving  dial  is  first  placed  at  the  zero  mark,  so 
that  no  focus  whatever,  either  spherical  or  cylindrical,  may  be 
before  the  e}'e  at  the  time  the  test  is  begun.  The  patient  is 
asked  to  name  the  lowest  letters  which  are  visible  on  the  card. 
In  myopia  he  will  be  able  to  see  only  the  largest  letters,  or  in 
high  degrees  none  at  all.  As  a  matter  of  precaution,  the  wheel 
is  turned  toward  convex  lenses,  which  at  once  throws  a  deeper 
blur  over  the  card  and  letters.  Then  the  rotation  is  made 
toward  concaves,  with  the  effect  of  brightening  and  clearing 
the  card,  and  the  degree  of  myopia  is  estimated  by  reading  the 


171 


graduation  on  tlic  indicator  after  the  focusing  adjustment  had 
been  turned  as  far  to  the  right  as  necessary  to  make  the  small 
letters  clear  and  distinct,  and  then  back  a  little,  if  possible, 
without  casting  a  blur  upon  them.  The  most  imjx)rtant  point, 
and  one  to  be  kept  constantly  in  mind  when  dealing  with 
myopia,  is  to  obtain  the  best  vision  with  the  instrument  so  ad- 
justed that  it  registers  the  very  smallest  amount  of  defect,  and 
to  prescribe  accordingly  the  weakest  glass. 


The  Refractometeh. 


Optoiiidcr. — This  instrument  consists  of  an  adjustable 
stand  supporting  a  horizontal  rod,  which  has  two  movable 
slides  for  holding  lenses,  with  a  test  card  at  the  far  end  and  an 
eye  shield  at  the  near  end.  To  measure  the  amount  of  myopia, 
a  concave  lens  of  8  D.  is  placed  in  the  clip  of  the  eye  shield 
and  a  convex  lens  of  the  same  strength  placed  in  the  slide  and 
moved  away  from  the  eye.  The  patient  looks  at  the  small  test 
card,  and  the  point  where  the  type  appears  brightest  will  in- 
dicate the  proper  correctiiig  lens,  as  shown  by  the  scale  marked 
on  the  rod. 


Pfisoptoiiu'lcr. — This  iiistnimeiit  rMiuains  a  doul^lc  ])risni. 
set  in  a  large  disk,  which  can  be  revolved  from  o  to  i<So  ,  and 
which  has  the  effect  of  doubling  all  objects  whicli  the  patient 
looks  at.  The  test  ol)ject  is  a  white  circular  disk  hanging  six- 
teen feet  awa\-.  and  if  the  ])crson  is  ennnetropic  the  two  disks 
seen  are  just  touching  each  other.  If,  however,  there  is  an 
excess  of  refraction,  as  in  myopia,  the  disks  will  overlap  and 
then  minus  lenses  must  be  placed  in  llie  holder  of  the  instru- 
ment to  separate  them,  and  that  lens  w  liich  makes  them  merel\ 
in  contact  will  be  the  measure  of  the  myopia. 

These  three  instruments  are  the  ones  in  most  conmion  use 
for  measuring  the  refraction  of  the  eye.     They  are  all  based  on 


OPTd.METEK. 


scientific  principles,  but  all  act  in  a  different  way.  Any  one 
or  all  of  them  would  prove  valuable  adjuncts  to  an  optician's 
outfit,  but  they  must  always  be  considered  as  subordinate  to 

the  test  case. 

scheiner's  test. 

Two  small  perforations. are  made  in  a  card  close  enough 
together  so  that  rays  passing  through  them  will  enter  the 
pupil.  The  patient  looks  at  a  candle  flame  twenty  feet  away, 
which  in  emmetropia  will  appear  single,  because  the  two  sets 
of  rays  passing  through  the  two  holes  exactly  meet  upon  the 
retina.  In  the  elongated  eye-ball  of  myopia  the  two  sets  of 
rays  will  have  united  and  crossed  before  reaching  the  retina, 
aiifi  as  these  diverging  sets  of  rays  strike  this  membrane  two 
images  of  the  flame  are  formed.  That  concave  lens  placed 
behind  the  card  which  fuses  the  two  images  into  one,  wall  be 
the  measure  of  the  amount  of  myopia.  In  this  defect  the 
two  images  are  homonymous  in  contrast  with  hypermetropia, 


MYOPIA.  173 

where  the  images  are  crossed.  In  order  to  determine  which 
form  is  present,  a  .red  glass  should  be  placed  in  front  of  one 
perforation,  and  if  the  flame  on  the  same  side  is  red  the 
diplopia  is  homonymous  and  the  case  one  of  myopia. 

CHROMATIC   TEST. 

This  test  depends  upon  chromatic  aberration,  or  the  un- 
equal refraction  of  the  different  colored  rays  of  which  white 
light  is  composed.  The  red  rays  being  the  strongest,  are 
turned  least  from  their  course,  and  the  violet  being  the  weak- 
est, are  deviated  most.  A  cobalt  lens  is  used  for  this  test,  be- 
cause it  suppresses  all  the  intermediate  colors  and  allows  only 
the  red  and  blue  to  pass.  The  blue  rays  being  more  strongly 
refracted,  are  brought  to  a  sooner  focus,  and  the  red  rays 
being  least  refracted  to  a  later  focus.  In  the  myopic  eye, 
where  the  retina  is  too  far  back,  it  approaches  the  position 
of  the  focus  of  red  rays,  whereas  the  blue  rays  have  already  met 
in  focus  and  strike  it  in  divergent  rays.  Hence  when  such 
an  eye  looks  through  such  a  lens  at  a  lighted  candle  twenty 
feet  away  the  flame  will  appear  of  a  distinct  red  center  with  a 
blue  border.  This  subject  has  been  illustrated  and  explained 
in  detail  on  pages  78,  79,  285,  286  and  287,  of  Volume  I. 

■      TREATMENT  OF  MYOPIA. 

As  the  one  thing  of  which  the  myopic  patient  will  chiefly 
complain  is  poor  vision  so  his  single  desire  is  to  get  glasses 
that  will  enable  him  to  see  well;  consequently  the  treatment 
of  myopia  by  the  refracting  optician,  and,  indeed,  the  prin- 
cipal remedial  measure,  even  in  the  hands  of  the  oculist,  con- 
sists in  the  careful  adaptation  of  the  proper  concave  glasses 
for  the  correction  of  the  anomaly.  To  afford  good  vision  both 
for  distance  and  reading,  as  well  as  to  prevent  unnecessary 
convergence,  requires  no  little  skill  on  the  part  of  the  optician. 
A  myopic  person  should  never  be  allowed  to  choose  his  own 
glasses,  because  he  is  apt  to  pick  out  those  that  are  too  strong 
and  thus  impose  an  extra  tax  upon  his  accommodation  (which 
in  this  defect  is  weaker  than  normal),  and  this  would  tend  to 
aggravate  and  increase  the  very  defect  which  he  is  endeavor- 
ing to  correct. 


]M 


TREATMENT  BY  CONCAVE  LENSES. 

The  first  stop  in  the  adjustment  of  glasses  for  the  correc- 
tion of  myopia  is  to  ascertain  the  acuteness  of  vision,  as  shown 
by  the  lowest  line  the  patient  can  read  on  a  Snellen's  test 
card,  hanging-  twenty  feet  away.  One  eye  is  to  be  tested  at 
a  time,  and  preferably  the  one  that  has  the  best  vision,  the 
other  being  covered  with  an  opaque  disk.  If  he  can  distin- 
guished only  the  largest  letter,  the  one  that  is  marked  200, 
his  visual  acuteness  equals  -f^^.  In  high  myopia  even  this 
large  letter  will  not  be  legible,  and  then  it  becomes  necessary 
to  place  the  card  at  a  closer  distance  or  allow  the  patient  to 
approach  the  card  until  the  No.  200  letter  becomes  readable, 
and  the  distance  at  which  it  is  first  seen  will  represent  the 
numerator  of  the  fraction  that  is  used  to  express  the  visual 
acuity.    For  instance,  if  he  has  to  come  as  close  as  eight  feec 

his  vision  would  equal  2-y-o.  ll 

The  patient  is  then  asked  to  resume  his  seat  at  twenty  feet 
from  the  card,  and  the  test  with  concave  lenses  commences. 
The  optician  having  satisfied  himself  that  the  case  is  one  of 
myopia,  places  a  weak  concave  lens  before  the  eye  and  notices 
how  much  improvement  in  vision  is  afforded.  Then  a 
stronger  and  a  stronger  is  tried,  until  that  one  is  found  that 
produces  the  greatest  amount  of  vision,  the  preference  in- 
variably being  given  to  the  very  weakest  glass  that  accom- 
plishes this  result.  It  is  always  better  in  myopia  to  err  on  the 
side  of  giving  a  glass  that  is  too  weak  than  one  too  strong. 

GLASSES   IN  LOW  MYOPIA. 

In  the  low  grades  of  myopia  as  2  D.  or  2.50  D.  or  less, 
the  glasses  are  necessary  only  to  enable  the  patient  to  get  a 
distinct  view  of  distant  objects.  At  school,  to  discern  the 
blackboard;  at  church,  to  see  the  preacher;  at  the  theatre,  to 
view  the  actors;  when  out  doors,  to  behold  the  scenery;  or 
any  occasion  when  it  is  desirable  to  see  distinctly  farther  away 
than  arm's  length;  in  a  word,  to  comprehend  the  world  and 
the  beauties  of  nature  and  art  as  other  people  do;  these  are 
the  purposes  fulfilled  by  glasses  in  the  slighter  degrees  of  this 
defect.    Of  course,  there  are  many  persons,  after  having  once 


MYOPIA.  175 

experienced  the  satisfaction  of  perfect  distant  vision  afforded 
by  the  concave  glasses,  who  are  unwilling  to  do  without  them 
and  get  into  the  habit  of  wearing  them  more  or  less  constantly 
even  in  doors  and  for  close  work. 

But  in  these  slighter  degrees  of  the  defect  the  use  of 
glasses  is  entirely  unnecessary  for  close  vision,  and  not  only 
so,  but  they  even  impose  a  strain  upon  the  accommodation, 
and  hence  should  be  removed  when  engaged  in  reading  or 
writing.  The  reason  for  this  is  obvious :  In  these  cases  vision 
is  perfectly  good  out  to  the  far  point,  which  is  situated  at 
eighteen  or  twenty  inches  from  the  eyes,  sufficiently  removed 
to  allow  of  good  vision  in  the  customary  close  use  of  the  eyes; 
such  being  the  case,  there  is  no  need  for  glasses,  and  especially 
as  instead  of  improving  vision  they  tend  to  impair  by  dimin- 
ishing the  size  of  the  retinal  image  and  calling  into  action  the 
ciliary  muscle.  Their  persistent  use  under  these  circumstances 
would  favoi  an  increase  in  the  error  of  refraction,  or  might 
even  give  rise  to  the  progressive  form  of  myopia,  which  is 
always  a  source  of  anxiety  to  both  optician  and  patient. 

GLASSES   IN   HIGH    MYOPIA. 

While  in  the  lower  grades  of  myopia  glasses  may  be  re- 
garded somewhat  as  a  luxury,  and  their  use  a  matter  of  indif- 
ference, in  the  higher  degrees  of  the  defect  they  become  an 
actual  necessity  and  cannot  be  safely  dispensed  with.  In  these 
cases  they  are  needed  not  only  to  improve  the  distant  vision, 
but  also  to  increase  the  reading  distance,  and  in  addition  they 
play  an  important  part  in  harmonizing  the  accommodation  and 
convergence  and  preventing  an  increase  of  the  defect. 

In  the  medium  degrees  of  myopia  (5  D.  or  less),  where 
the  patient  is  not  old  and  the  range  of  accommodation  good, 
the  full  correction,  as  a  general  rule,  may  be  allowed.  But 
in  the  higher  grades  two  pairs  of  glasses  must  be  prescribed, 
because  the  glasses  needed  for  the  full  correction  are  entirely 
too  strong  for  close  work  and  impose  an  unnecessary  and  un- 
bearable tax  upon  the  accommodation,  and  then  the  question 
naturally  arises  as  to  what  is  the  proper  strength  of  glass  to 
adopt  in  each  particular  case? 


1'C,  MYOPIA. 

Without  "lasses  tlic  myope  is  compelled  to  hold  his  book 
imnaturalh'  close,  which  is  not  only  very  uncomfortable,  but 
in  addition  proves  a  source  of  strain  to  the  function  of  con- 
vergence. If  he  wears  his  full  correction  glasses,  the  lessen- 
ing in  the  size  of  the  retinal  image  by  the  strong  concave 
lenses,  and  the  impairments  in  the  function  of  the  retina  due 
to  the  stretching  which  it  has  undergone,  originate  and  en- 
courage a  desire  to  bring  the  object  nearer  to  the  eye  in  order 
to  obtain  a  larger  visual  angle.  In  the  first  case  there  is  ten- 
sion of  accommodation  and  convergence,  the  greatest  strain 
being  on  the  latter;  in  the  second  case  there  is  a  similar  ten- 
sion of  both  functions,  but  now  the  greater  strain  is  upon  the 
former.  Between  two  evils,  the  proper  plan  is  to  choose  the 
least,  but  a  still  better  method  is  to  avoid  both  of  them  if  pos- 
sible. In  this  case  it  might  be  difficult  to  decide  which  was' 
the  greater  evil  of  the  two — the  strain  upon  the  accommoda- 
tion or  upon  the  convergence,  but  the  way  is  open  by  which 
both  in  a  measure  can  be  avoided. 

RULE    FOR    DETERMINING    THE    READING    GLASSES    IN    MYOPIA. 

Instead  of  allowing  the  patient  tO'  read  with  his  full  cor- 
rection glasses  we  select  a  pair  which  only  partly  neutralizes 
the  error  of  refraction,  or  in  other  words  those  glasses  which 
remove  the  far  point  to  a  convenient  reading  distance  of 
twelve  to  fifteen  inches.  The  rule  may  be  expressed  some- 
what as  follows:  Subtract  from  the  glasses  zuhich  are  the  full 
measure  of  the  myopia  those  glasses  tlie  focus  of  zvhich  represents 
the  distance  at  which  the  patient  desires  to  read  or  zuork. 

As  thirteen  inches  is  regarded  as  a  proper  reading  dis- 
tance, and  as  a  glass  of  +  3  D.  represents  a  distance  of  thirteen 
inches,  therefore  it  is  customary  to  subtract  about  3  D.  from 
the  full  measure  of  the  defect  in  order  to  arrive  at  the  correct 
glasses  for  close  use.  In  some  cases  it  may  be  desirable  to 
subtract  a  little  more  and  in  some  cases  a  little  less,  depend- 
ing on  the  age,  the  amount  of  available  accommodation  and 
the  distance  at  which  the  patient  desires  to  use  the  glasses. 
This  point  can  readily  be  determined  by  the  trial  of  several 
numbers  slightly  weaker  and  slightly  stronger  than  those  in- 
dicated by  the  above  rule,  and  the  choice  being  given  to  that 


MVoriA.  i;V 

one  that  affords  the  most   satisfactory  vision  at  the  distance 
desired. 

Finall}-,  the  i^Iasscs  must  he  sul^niitted  to  the  test  of  actual 
experience,  and  the  patient,  after  a  few  weeks'  trial,  will  be 
able  to  say  whether  they  are  pleasant  or  unsatisfactory, 
whether  the  eyes  are  conifortable  or  whether  symptoms  of 
asthenopia  have  been  provoked,  and  thus  will  be  decided  the 
question  as  to  the  suitableness  of  the  grlasses  for  continued 
wear  or  whether  they  should  be  changed  for  others  of  a  dif- 
ferent power.  Sometimes  no  glasses  can  be  found  vvhich 
render  near  vision  entirely  comfortable,  and  then  it  becomes 
necessary  for  the  person  to  abandon  all  work  or  occupation 
requiring  close  use  of  the  eyes. 

In  high  myopia,  if  the  person  had  not  previously  worn 
glasses  it  is  inadvisable  to  prescribe  the  full  correction  at  first, 
because  such  strong  glasses  are  unpleasant  and  they  are  apt 
to  disturb  the  relative  association  of  accommodation  and  con- 
vergence. In  these  cases  the  better  plan  is  to  commence  with 
weaker  numbers  and  gradually  increase  their  strength  from 
time  to  time,  as  the  eyes  become  accustomed  to  them,  until 
finally  the  full  correction  can  be  worn  for  distance  without 
producing  unpleasant  symptoms  or  injurious  disturbances. 

It  is  important  that  the  patient,  and  still  more  so  the 
optician,  should  have  a  clear  idea  of  the  purposes  for  which 
the  reading  glasses  are  prescribed  in  myopia.  They  are  not 
intended  so  much  to  magnify  the  print  or  enable  the  person 
to  see  better  (in  fact,  concave  lenses  necessarily  minify  objects 
seen  through  them)  as  to  increase  the  distance  at  which  read- 
ing can  be  accomplished  to  enable  the  person  to  read  at  the 
customary  distance  and  thus  relieve  the  strain  upon  the  con- 
vergence. If  the  old  habit  of  holding  objects  close  to  the  eyes 
is  still  continued,  then  reading  glasses  are  not  only  useless 
but  positively  harmful.  Hence  the  importance  of  impressing 
upon  the  patient  the  necessity  of  keeping  the  book  as  far 
away  as  the  glasses  will  allow. 

There  can  be  no  fixed  rules  by  which  glasses  should  be 
adjusted  in  every  case,  but  each  nnist  be  treated  uix>n  its  own 
merits.  Many  myopes  wear  their  full  correction  constantly, 
both  for  near  and  distance,  without  '^nffering  anv  inconveni- 


178  MvoriA. 

eiioe  ami  apiiarcnily  without  any  injur\-  to  their  eves,  while 
others  can  scarcely  hear  their  correction  for  distance  much  less 
for  reading". 

While  the  writer  was  penning-  these  lines  a  patient  con- 
sulted him,  thirty-five  years  of  age  and  wearing  —  6.50  D. 
glasses.  Has  worn  these  same  glases  for  twenty-three  years, 
usin,g  them  for  all  purposes,  near  and  far,  and  without  any 
difficulty.  Recently  has  suffered  from  headache,  which  he  at- 
tributes to  an  attack  of  la  grippe,  but  his  physician  advised 
him  to  ct)nsult  an  oculist.  On  examination  1  was  surprised 
to  find  a  myopia  of  onl\-  5  1).  in  R.  li.  and  4  D.  in  L.  E.  The 
remarkable  point  about  this  case  is  that  his  glasses  should  have 
been  so  comfortable  for  close  work  all  these  years,  in  spite  of 
the  fact  that  this  defect  was  over-corrected  (thus  rendering-  his 
eyes  really  hypermetropic)  and  that  he  was  approaching-  the 
time  of  life  when  a  lessened  accommodation  would  call  for  a 
weaker  concave  lens. 

DOXDEKS"    .\1)V1C1-:. 

In  discussing-  the  importance  of  the  proper  selection  of 
glasses  in  individual  cases  of  myo]>ia.  Bonders'  remarks  are 
so  apropos  that  they  are  worthy  of  re])roduction  on  these 
pages,  and  especially  as  everything  issuing  from  the  mouth 
or  pen  of  this  gifted  man  is  universally  accepted  as  gospel  truth 
by  all  seekers  after  optical  knowledge,  alike  by  oculists  and 
opticians.  He  savs:  "The  prescribing  of  spectacles  for  mv- 
opes  is  a  matter  of  great  importance.  While  emmetropic  and 
hypermetropic  eyes  do  not  readily  experience  any  injury  from 
the  use  of  unsuitable  glasses,  this  may  in  myopes,  particularly 
on  account  of  the  morbidly  distended  condition  of  the  eye-ball 
and  of  the  tendency  to  get  worse,  be  very  dangerous.  There 
exists  in  general  a  dread  of  the  use  of  too  strong  glasses.  It 
is  laid  dowai  as  a  rule:  Rather  too  w^eak,  or  no  glasses,  than  too 
strong.  In  this  rule  the  necessary  distinction  is  lost  sight  of. 
Too  strong  glasses  make  hypermetropic  eyes  myopic,  and  my- 
opic eyes  hypermetropic.  The  rule  therefore  cannot  be 
equally  true  for  both.  In  fact  it  is  in  general  much  less  in- 
jurious to  produce  a  certain  degree  of  mvopia  than  of  hvper- 


MVOPIA.  179 

nietroi)ia,  in  which  last  particularly  much  is  reciuired  of  the 
accommodative  power.  Jhe  rule  would  therefore  be  more 
correctly  stated  thus:  in  hypermetropia  we  must  beware  of 
^ivino-  too  weak;  in  myopia  of  Skiving-  too  strong-  glasses;  a 
ndc  the  second  part  of  which  we  should  especially  insist  upon. 
l')Ut  even  by  this  little  is  gained.  Xot  using  glasses,  or  using 
too  weak  glasses,  may  also  be  injurious  to  myopes.  All  the 
circumstances  must  therefore  be  studied,  which  can  exercise  an 
influence  on  the  choice  of  glasses.  It  is  difificidt  to  reduce 
these  to  definite  rules."' 

A    PERSONAL   EXPERIK.VCK   WITH    CONCAVE   GLASSES. 

M.  Sarcy.  a  well-known  h'rench  critic,  had  congenital 
myopia,  and  in  later  life  became  temporarily  blind.  In  one 
eye  he  suffered  a  retinal  detachment,  and  in  the  other  a  cata- 
ract. By  means  of  an  operation  vision  in  the  latter  eye  was 
restored  and  became  better  than  ever.  He  relates  an  inter- 
esting bit  of  personal  experience  in  the  following  words: 

"I  was  born  near-sighted;  nian\-  physicians  assert  that 
persons  are  never  born  near-sighted,  and  only  become  so. 
Science  may  say  what  it  pleases;  T  was  born  myopic.  One 
day,  prompted  by  a  spirit  of  mischief,  I  got  hold  of  the  big 
silver  spectacles  which  my  father  wore  and  clapped  them  on. 
Fifty  years  have  passed  since  then,  but  the  sensation  I 
experienced  is  keen  and  thrilling  to  this  day.  I  gave  a  cry  of 
astonishment  and  joy.  Up  to  that  moment  I  had  seen  the 
leafy  dome  above  me  only  as  a  thick  green  cloth,  through 
which  no  ray  of  sunshine  ever  fell;  now,  oh  wonder  and  de- 
light! I  saw  that  in  this  dome  were  many  little  brilliant 
chinks;  that  it  was  made  of  myriad  separate  and  distinct  leaves, 
through  whose  interstices  the  sunlight  sifted,  imparting  to  the 
greenery  a  thousand  forms  of  light  and  shade.  I'.ut  what 
amazed  me  most,  what  enchanted  me  so  that  1  caimot  speak 
of  it  to  this  day  without  emotion,  was  that  1  saw  suddenly, 
between  the  leaves  and  far,  far  away  beyond  them  little 
glimpses  of  the  bright,  blue  sky.  I  clapped  my  haiuls  in 
ecstasy  and  was  mad  with  astonishment  and  delight." 


180 


HOW  MVOriA   DISTURBS  THE   NORMAL   RELATION    EXISTING   BE- 
TWEEN   ACCOMMODATION    AND    CONVERGENCE. 

The  far  ix)int  of  a  myope  is  always  situated  at  a  finite 
distance,  and  is  determined  by  the  degree  of  the  defect.  A 
myope  of  4  D.  has  a  far  point  of  ten  inches,  and  can  see  at 
that  distance  without  any  effort  of  accommodation,  but  he 
must  converg-e  four  meter  angles  in  order  to  maintain  binocu- 
lar vision.  Now,  in  the  case  of  an  emmetropic  eye  the  accom- 
modation and  convergence  are  used  in  equ^l  proportion,  and 
hence  a  distance  of  ten  inches  would  call  for  4  D.  of  accom- 
modation and  four  meter  angles  of  convergence. 

Therefore  in  myopia  the  convergence  is  necessarily  used 
in  excess  of  the  accommodation,  a  condition  just  the  reverse  of 
hypermetropia  where  the  accommodation  is  used  in  excess  of 
the  convergence.  Nature  will  allow  to  a  certain  extent  the 
use  of  one  function  in  excess  of  the  other  as  a  result  of  nerve 
education,  but  she  inflicts  a  penalty  for  this  as  shown  by  the 
frequency  of  "eye  strain"  under  these  conditions. 

In  myopia  the  fusion  efifort  must  be  greater  than  in  em- 
metropia,  and  the  greater  this  effort  the  more  the  fatigue  of 
the  internal  recti  muscles;  this  fatigue  leads  to  "insuf^ciency" 
of  the  muscles  and  thus  matters  are  made  worse.  A  myope 
requires  more  convergence  of  the  visual  lines  because  vision 
takes  place  so  close  to  the  eyes,  and  this  is  particularly  difificult 
in  this  defect  on  account  of  the  elongated  shape  of  the  eye-ball 
which  impedes  its  movements.  There  may  be  no  actual  weak- 
ness of  the  internal  recti  muscles,  but  only  apparently  so  on 
account  of  the  excess  of  work  they  are  called  upon  to  perform. 

DIVERGENT   STRABISMUS. 

In  the  previous  chapter  it  was  shown  that  hypermetropia 
was  the  direct  cause  of  a  majority  of  the  cases  of  convergent 
squint.  And  as  myopia  is  a  condition  of  the  eye  exactly  the 
reverse  of  hypermetropia,  it  will  be  found  that  many  of  the 
cases  of  divergent  squint  occur  in  connection  with  near-sight- 
edness. The  accommodation  is  used  but  little,  while  the  con- 
vergence must  be  excessive,  which  latter  continues  until  the 
eyes  have  reached  the  maximum  state  of  convergence,  and 
then  the  energv  and  tone  of  the  internal  recti  muscles  sooii 


MvoriA.  181 

become  exhausted,  and  as  it  tires  and  gives  way  the  eye  turns 
outward.  The  power  of  accommodation  still  remains  unim- 
paired, but  the  power  of  convergence  is  worn  out,  because  the 
limit  within  which  the  two  functions  may  vary  has  been  over- 
stepped. 

As  soon  as  the  object  is  brought  nearer  than  the  extreme 
limit  of  convergence  in  binocular  vision  will  permit,  divergent 
strabismus  necessarily  takes  place,  and  this  may  occur  even  if 
there  be  no  actual  insufficiency  of  the  internal  recti  muscles, 
just  as  in  hypermetropia  there  may  be  no  actual  weakness  of 
the  ciliary  muscle;  but  simply  that  in  each  case  the  muscles 
have  laid  upon  them  work  which  is  beyond  their  power  to 
perform.  While  the  convergent  strabismus  of  hypermetropia 
usually  makes  its  appearance  in  childhood,  the  divergent 
squint  of  myopia  is  rarely  developed  until  a  more  advanced 
age,  and  is  usually  connected  with  the  progressive  form  of  the 
defect. 

If  the  myopia  develops  slowly,  the  internal  recti  muscles 
may  gradually  increase  in  size  and  strength  sufficiently  to  per- 
form the  excessive  labor  demanded  of  them,  but  usually  there 
is  a  deficiency  of  power  of  one  or  both  of  these  muscles  to 
maintain  the  required  convergence  for  any  length  of  time,  and 
especially  if  the  progress  of  the  myopia  has  been  rapid.  In 
such  cases  the  internal  recti  muscles  are  too  weak  to  resist  the 
action  of  the  external,  and  the  eye  rolls  outward  and  double 
vision  results.  When  once  an  insufficiency  of  the  internal 
recti  has  manifested  itself,  the  muscles  do  not  readily  regain 
their  strength  even  after  considerable  periods  of  rest ;  they  be- 
come less  and  less  able  to  sustain  prolonged  action,  until 
finally  the  insufficiency  becomes  so  annoying  that  artificial 
assistance  must  be  sought  or  binocular  vision  abandoned. 

TREATMENT  OF  THE  MUSCULAR  INSUFFICIENCY  ACCOMPANYING 
MYOPIA. 

Insufficiency  of  the  internal  recti  muscles  is  usually  found 
in  cases  of  myopia  ranging  from  4  D.  to  7  D.,  and  when  it 
occurs  the  advice  is  at  once  gratuitously  offered  by  all  the 
friends  to  rest  the  eyes,  which  the  patient  is  inclined  to  adopt 
because  it  affords  temporary  relief.     If  these  muscles  are  not 


1S2  MvoriA. 

straineil.  naturally  they  will  cease  to  ache.  But.  as  in  the  case 
of  all  other  muscles,  if  they  are  not  used  they  undergo  loss  of 
tone,  and  hence  the  more  they  are  rested  the  less  they  will  be 
able  to  work.  Therefore  the  common  prescription  of  rest  is 
bad.  unsoimd  in  principle  and  disastrous  in  practice.  The 
writer  has  seen  cases  of  this  kind  who  could  not  use  their  eyes 
at  all,  where  reading  for  only  a  minute  brought  on  pain  and 
lachrymation.  Such  persons  being  debarred  from  reading  and 
almost  every  use  of  the  eyes,  have  nothing  to  do  but  to  dwell 
upon  their  own  troubles,  and  they  are  constantly  worried  by 
the  fear  they  will  some  day  become  blind. 

The  proper  principle  to  adopt  in  the  management  of  these 
cases  is  to  train  and  strengthen  the  muscles  by  discreet  use 
and  by  gymnastic  exercises.  The  right  lenses  for  reading  are 
carefully  chosen  according  to  the  directions  already  given,  and 
then  they  must  be  accorded  a  patient  trial  to  see  how  far  or 
how  long  their  use  is  practicable.  By  increasing  the  reading 
distance  these  glasses  lessen  the  efifort  of  convergence,  which 
is  thus  made  more  nearly  equal  with  the  accommodation.  If. 
however,  this  method  fails  to  afford  the  desired  relief  it  may 
become  necessary  to  combine  prisms. 

In  the  slighter  degrees  of  myopia,  some  authorities  recom- 
mend that  the  glasses  should  be  worn  constantly,  for  the  follow- 
ing reasons:  In  this  way  the  eyes  are  practically  made  emme- 
tropic; the  accommodation  is  brought  into  action  instead  of 
allowing  it  to  remain  idle;  there  is  no  occasion  to  hold  the  book 
close,  a  habit  which  has  much  to  do  in  the  causation  and  aggra- 
vation of  myopia.  Priestley  Smith  says:  "My  present  custom 
is  to  encourage  rather  than  discourage,  with  proper  limits,  the 
use  of  the  accommodation;  in  other  words,  to  advise  those 
whjo  can  to  use  the  same  glasses  for  reading  and  distance,  and 
where  this  is  impossible,  by  reason  of  weak  accommodation, 
still  to  give  reading  glasses  as  strong  as  can  be  worn  with 
comfort." 

The  full  correction  of  the  myopia  restores  the  harmony 
between  the  functions  of  accommodation  and  convergence,  a 
procedure  which  may  be  quite  practical  in  young  persons,  but 
for  this  very  reason  in  older  patients  it  is  not  well  borne.  The 
habit  of  converging  in  excess  of  accommodation  has  become 


MYOPIA.  183 

SO  fixed  for  so  many  years,  that  it  c-aiinot  cvi-n  l)y  practice  he 
easily  relaxed,  and  under  sueh  eireunistanees  if  the  wearing'  of 
the  glasses  he  insisted  u])()n.  lhe\  may  hecome  a  cause  of  eye 
strain  instead  of  a  means  for  its  removal. 

I'or  such  persons,  if  the  myo])ia  l)e  less  than  5  1).,  the 
wearing  of  glasses  for  distance  will  he  all  that  is  necessary. 
As  a  matter  of  fact  there  are  many  persons  with  a  myo|)ia  of 
3  D.  or  less,  who  never  use  glasses  at  all;  the\-  are  not  incon- 
venienced hy  the  ])artial  indistinctness  of  distant  vision,  which 
is  scarcely  marked  enough  to  ])revent  the  recognition  of 
ordinary-sized  ohjects.  while  their  near  wDrk  can  be  accom- 
plished at  the  usttal  distance  without  any  strain  upon  the  eye. 

Till-:  ()Tiii:k  sidI':  oi-    iiii-;  (jii-.siiox. 

Landolt's  views  are  somewhat  dilTerent  from  those  given 
above;  he  says:  ".\  myope  must  he  prohibited  from  wearing 
a  concave  glass  for  any  distance  at  which  he  can  see  clearly 
without  accommodation.  Correcting  glasses  have  a  very 
serious  disadvantage  for  the  myoi)e,  because  they  force  him 
to  make  an  effort  of  acconunodation  from  which  his  ametropia 
grants  him  dispensation,  and  the\-  de])rive  him  oi  another  ad- 
vantage, /.  c,  of  the  larger  size  of  the  retinal  images  obtained 
by  the  naked  eye,  and  which  the  glasses  make  smaller." 

After  all,  each  case  nuist  l>e  managed  on  its  own  merits; 
on  the  one  hand  we  must  avoid  an  overtaxing  of  the  accom- 
modation by  a  too  strong  concave  lens,  and  on  the  other  hand 
we  must  prevent  the  strain  of  excessive  convergence,  because 
the  stooping  position  of  the  head  which  accompanies  it  favors 
congestion  and  leads  to  increased  intraocular  pressure,  and 
thus  tends  to  the  increase  of  the  defect.  With  this  view,  the 
concave  glasses  that  lengthen  the  reading  distance  to  twelve 
or  fifteen  inches,  j^lay  an  imp(-)rtaut  part  in  relieving  eye  strain 
and  jireventing  increase  of  the  myopia. 

MlSl  I.K   TKSTS. 

In  order  to  determine  the  relative  or  absolute  weakness  of 
the  internal  recti  nmscles,  a  trial  should  he  made  to  see  what 
strength  of  prism  they  are  able  to  overcome.  I'or  this  pur- 
pose the  patient  looks  at  a  lighted  candle  placed  at  a  distance 


184  MYOPIA. 

of  twenty  fcrt.  'I'licii  ;i  wi-ak  ])risni  is  placed  l)rf( )!■(.'  one  eve. 
base  out,  cansin*^'  a  nii>nientar\"  (liploi)ia.  which  soon  disap- 
pears. Now  a  similar  prism  is  placed  before  the  otlier  eye, 
with  a  like  result.  This  is  repeated  with  increasing-  prisms 
until  the  double  images  of  the  candle  llanie  can  no  longer  lie 
united  into  one  by  any  muscular  effort. 

If  it  is  found  the  muscles  can  thus  overcome  a  ])air  of 
prisms  of  12°  each  (makings  a  total  of  24"),  they  cannot  be  con- 
sidered as  deficient  in  strength,  and  the  prismatic  element  will 
scarcely  need  to  be  added  to  the  necessary  concave  lenses,  the 
use  of  which  alone  may  be  all  that  is  necessary  tO'  restore  the 
normal  relation  between  accommodation  and  convergence, 
and  thus  relieve  all  the  eye  symptoms.  Such  use  of  the  eyes 
may  be  regarded  as  gymnastic  exercise,  to  be  stopped  before 
it  produces  undue  fatigue,  and  to  be  resumed  at  regular  inter- 
vals. Sometimes  there  will  be  a  good  deal  of  pain  at  first, 
especially  with  nervous  persons  and  those  who  have  been  try- 
ing the  "rest"  cure,  but  they  nuist  be  encouraged  to  persevere 
jiotwithstanding. 

If,  however,  the  internal  recti  muscles  cannot  overcome 
the  diplopia  caused  by  a  pair  of  prisms  of  12°,  bases  out,  they 
must  then  be  regarded  as  absolutely  weak,  in  whicli  case  it  may 
become  necessary  to  combine  prisms  in  order  to  assist  and 
strengthen  them. 

In  cases  of  high  myoipia  (that  is,  from  6  D.  to  20  D.)  the 
eyes  are  often  saved  the  convergence  effort  at  the  expense  of 
binocular  vision ;  that  is  to  say,  the  person  uses  only  one  eye 
for  vision  and  the  other  squints  outwardly.  If  such  a  con- 
dition has  continued  long  enough  to  become  a  confirmed  habit, 
it  is  scarcely  worth  while  to  attempt  to  correct  it;  in  fact,  it  is 
an  almost  impossible  task  to  restore  binocular  vision  and  cause 
the  two  eyes  to  work  in  harmony.  In  many  of  these  cases 
it  will  be  found  on  examination  that  one  eye  is  used  chiefly 
for  reading  and  the  other  principally  for  distance,  and  to  make 
the  effort  to  disturb  such  an  arrangement  oftentimes  does  more 
harm  than  good,  and  here  the  optician  must  be  content  to  give 
the  proper  glass  to  each  eye  for  its  own  particular  use. 

In  contrast  with  the  24°  prism,  which  the  eyes  can  over- 
come when  placed  base  out,  we  find  that  not  more  than  6'  ov 


18: 


8°  can  be  borne  when  placed  base  in.  This  marked  difference 
is  owing  to  tlie  fact  that  in  the  first  case  the  internal  recti 
muscles  are  brought  into  action,  and  in  the  second  case  the 
external,  and  that  the  former  are  so  nuich  stronger  than  the 
latter  because  they  need  to  be  used  so  much  more. 

When  it  comes  to  prisms  being  placed  vertically,  but  very 
few  persons  can  overcome  more  than  i°  or  2°,  because  the 
superior   and    inferior   recti    muscles   are   relatively   so    much 


weaker  than  either  the  internal  or  external  recti.  The  nomen- 
clature of,  and  the  tests  for,  the  various  muscular  anomalies 
have  been  described  in  the  chapter  on  "Method  of  Examina- 
tion," to  which  the  reader  is  referred. 


A 11  USE  OF  THE    KVES. 

The  eye,  like  any  other  organ  of  the  body,  and  in  the 
same  manner  as  any  delicate  instrimient.  may  become  the  sub- 
ject of  abuse,  the  bad  effects  of  which  are  most  noticeable 
during  its  growing  period.  The  coats  of  the  eye-ball  do  not 
reach  their  full  measure  of  firmness  and  power  of  resistance 
until  adult  age.  about  the  twentieth  year  of  life,  the  time  when 
the  rest  of  the  body  arrives  at  maturity. 

Consequently  before  this  age,  and  particularly  between 
the  ages  of  six  and  sixteen,  during  what  may  be  called  the 
school  years,  the  eye  is  liable  to  injury  from  overwork.     This 


186  MYOPIA. 

results  (as  has  been  stated  earlier  in  the  chapter)  in  the  pro- 
duction of  myopia.  After  the  twentieth  year  of  life  the  eyes 
nia\  be  abused  in  many  ways  by  overwork  and  insuflficient 
or  im])roper  lio-ln  without  much  danger  of  causing  myopia. 
One-fourth  of  the  same  application  of  the  eyes  at  the  ag^e  of  ten, 
with  its  coats  and  contents  soft  and  yielding-,  would  cause  the 
])osterior  wall  to  give  way  and  bulge  and  bring  about  the  defect 
of  mvopia.  Whereas  when  the  eye  is  well  hardened  by  full 
growth  a  nuicli  greater  amount  of  eye  application  can  be  borne 
continuously  without  the  fear  of  causing  the  walls  of  the  eye 
to  stretch  and  injuriously  changing  the  shape  of  the  organ. 
Hence  the  fact  obtains  that  the  danger  of  the  i)roductit>n  of 
myopia  by  abuse  of  the  eyes  is  peculiar  to  youth  and  to  its 
growing  state. 

We  sometimes  meet  persons  having  a  slight  degree  of 
myopia  who  are  so  little  inconvenienced  by  it  that  they  are 
not  conscious  of  being  near-sighted:  in  fact,  consider  their 
vision  as  up  to  the  normal  standard.  The  existence  of  the 
defect  may  be  accidentally  discovered  by  contrast  with  the 
sharper  sight  of  some  friend,  or  by  casually  trying  on  a  pair  of 
concave  glasses  which  happened  to  be  in  their  w^ay,  and  which 
brightened  up  distant  vision  to  such  an  extent  as  they  never 
before  believed  possible. 

Others  may  complain  of  their  near-sightedness,  calling 
attention  only  to  the  fact  that  they  are  compelled  to  hold  their 
book  very  close,  but  never  making  mention  of  their  inability 
to  see  distant  objects. 

CORRECTION  OF  MYOPIA. 

The  correction  of  myopia  is  by  means  of  concave  lenses 
properly  adapted,  and  the  manner  in  which  they  act  can  be 
readily  understood.  It  will  be  remembered  that  in  this  defect 
parallel  rays  of  light  meet  in  front  of  the  retina;  if  now  the 
focus  can  be  thrown  back  just  far  enough  to  correspond  ex- 
actly to  the  location  of  the  retina,  then  and  only  then  does 
clear  distant  vision  become  possible.  This  is  accomplished  by 
means  of  concave  lenses,  which  spread  the  rays  of  light  and 
cause  them  to  enter  the  eye  divergently,  and  then  (the  refrac- 
tive power  of  the  eye  remaining  the  same)  thy  will  not  meet 


MvoriA.  187 

in  focus  so  soon  as  the  parallel  rays;  this  is  equivalent  to  throw- 
ing the  focus  farther  back,  and  if  the  concave  lens  corresponds 
with  the  degree  of  myopia  the  focus  will  he  exactly  upon  the 
retinal  surface. 

I'KAC  TICAf.    I'OIX'IS. 

In  myopia,  up  to  a  certain  degree,  there  is  usuall\  no  dis- 
turbance of  close  vision,  but  when  it  exceeds  5  1).  then  there 
is  apt  to  be  some  trouble  in  reading. 

In  the  higher  degrees  there  is  no  distinct  vision  beyond 
a  few  inches  from  the  eyes,  and  consequently  as  such  a  myope 
cannot  fix  objects,  his  eyes  assume  a  peculiar  far-away  look. 

In  the  slighter  degrees  the  only  inconvenience  suffered  is 
a  limitation  of  distant  vision,  so  that  if  the  ])erson  does  not 
wish  to  wear  glasses  no  very  great  harm  is  done,  only  the  loss 
of  pleasure  of  seeing  the  world  quite  as  distinctly  as  other  peo- 
ple see  it.  The  reading  limit  is  not  interfered  with,  as  the 
measure  of  the  myopia  (say  2  D.)  indicates  that  the  person  is 
able  to  read  as  far  away  as  twenty  inches,  and  therefore  in  these 
cases  there  is  no  occasion  to  hold  the  book  close,  but  it  may 
be  kept  at  the  usual  reading  distance  where  there  is  no  very- 
great  demand  made  upon  either  the  accommodation  or  con- 
vergence. But  it  is  just  in  this  class  of  cases  that  the  precau- 
tion should  be  taken  to  guard  against  any  inclination  to  hold 
the  book  too  close  or  to  read  by  any  kind  of  insufficient  light 
on  account  of  the  imminent  danger  of  increasing  the  myopia 
by  these  means. 

Floating  specks  before  the  eyes,  sparks.  Hashes  of  light, 
white  or  colored  rings,  are  not  uncommon  in  this  defect,  and 
they  are  apt  to  cause  the  patient  a  great  deal  of  uneasiness; 
but  they  arc  not  usually  of  any  special  pathological  import. 

HKXJAMIX    FRANKLIN,   TIIK   OKIC.INAL   1UI-<)CA1.   MAN. 

Tn  myopia  the  effects  of  presbyopia  are  not  felt  at  the 
usual  time,  perhaps  not  until  the  age  of  fifty-five  or  sixty ;  but 
when  it  does  manifest  itself,  there  is  the  double  inconvenience 
of  needing  glasses  for  both  distance  and  reading.  This  annoy- 
ance would  be  felt  by  clergymen,  lecturers,  and  others  who 
might  desire  to  look  at  the  book  in  their  hand  one  moment, 
and  then  to  lo«^k  at  the  audietice.  some  of  whom  might  be  at 


188  MYoriA. 

a  distance  of  fifty  feet  or  more.  This  was  the  case  of  Ben- 
jamin I'Vanklin,  and  as  he  was  a  very  busy  man  and  could  ni>t 
aflford  to  waste  so  much  time  as  niiglit  be  required  to  con- 
stantly change  his  glasses  if  he  wore  separate  pairs  for  reading- 
and  distance,  he  had  made  to  his  order  a  pair  of  spectacles 
which  contained  in  the  one  frame  both  pairs  of  glasses,  known 
as  divided  or  double  focus  spectacles,  and  he  was  the  first  to 
wear  this  form  of  spectacles,  which  are  so  common  at  the 
present  daw 

The  eyes  should  be  examined  at  intervals,  perhaps  once 
a  year,  to  determine  tBe  degree  of  myopia,  so  that  if  there  is 
any  tendency  to  an  increase  of  the  defect,  it  may  be  at  once 
detected.  Spectacles  should  be  worn  for  distance,  or  for  dis- 
tance and  reading  as  may  be  indicated,  with  the  proviso  that 
the  book  be  kept  well  away  from  the  eyes,  not  allowing  it  to 
get  any  nearer  than  eighteen  inches,  except  in  aggravated 
cases  where  such  a  reading  distance  is  impossible  even  with 
the  most  suitable  lenses. 

STRAIN   ON   THE   ACCOMMODATION. 

When  a  near-sighted  person  is  given  a  pair  of  concave 
lenses  of  sufficient  strength  to  completely  correct  his  defect, 
the  eyes  are  thereby  rendered  emmetropic,  and  when  reading- 
is  attempted  with  these  glasses  the  accommodation  is  called 
upon  for  the  same  amount  of  effort  as  in  a  normal  eye.  But 
as  has  already  been  stated  the  accommodation  in  myopic  eyes 
is  always  feeble,  the  more  so  the  higher  the  degree  of  defect, 
and  hence  it  is  not  equal  to  the  task;  so  that  to  ask  such  a 
person  to  read  through  concave  glasses  of  full  correction  is 
to  expect  an  impossibility;  or  else  it  is  accomplished  at  the 
expense  of  a  great  strain  upon  the  accommodation,  which  is 
lessened  if  the  book  be  held  at  an  inconveniently  great  dis- 
tance from  the  eyes. 

There  is  one  thing  about  concave  glasses  of  which  patients 
frequently  complain,  and  that  is  they  make  everything  seem 
smaller.  This  is  partly  real  and  partly  comparative.  Concave 
lenses  have  the  property  of  making  objects  smaller  just  as 
convex  lenses  magnify  them.  But  besides  this,  to  the  uncor- 
rected myopic  eye  on  account,  of  its  increased  refractive  power 


MYOPIA.  189 

objects  appear  larger  tlian  they  really  are  and  their  outlines 
imperfect;  concave  lenses  concentrate  the  sight,  make  the  out- 
lines of  objects  distinct,  and  in  contrast  with  tlic  former  vision, 
smaller. 

SURGICAL   TREATMENT    OF    MYOPIA. 

This  chapter  would  be  incomplete  without  some  reference 
to  the  surgical  treatment  of  myopia,  that  is,  the  removal 
of  the  crystalline  lens  for  the  purpose  of  reducing  the  exces- 
sive refraction.  It  cannot  be  denied  that  in  theory  this  method 
of  treatment  is  most  excellent,  and  forms  an  ideal  way  of  neu- 
tralizing the  defect.  While  it  is  sound  in  theory  and  feasible 
in  practice,  and  attractive  to  the  ophthalmic  surgeon  who  is 
making  a  brilliant  reputation  by  skillful  operations,  yet  when 
it  is  considered  entirely  from  the  patient's  standpoint  it  will 
scarcely  become  a  popular  procedure. 

Unlike  a  strabismus  operation  which  does  not  open  the 
cavity  of  the  eye-ball,  the  removal  of  the  crystalline  lens  is  a 
most  serious  matter  and  violently  disturbs  the  normal  condi- 
tion of  the  organ  of  vision.  The  parts  most  affected  are  the 
ciliary  region  and  adjoining  portions,  a  region  which  is  par- 
ticularly liable  to  inflammatory  reaction  after  injury  or  opera- 
tion. This  is  shown  in  the  history  of  cataract  onerations,  where 
an  occasional  eye  will  go  wrong  without  any  apparent  cause 
and  in  spite  of  every  precaution  i:)cing  taken  to  avoid  such  a 
calamity. 

A  case  of  myopia  and  one  of  cataract  have  no  points  in 
common.  The  latter  has  practically  lost  his  sight  and  there 
is  only  one  means  by  which  it  can  be  restored,  and  hence  while 
he  has  everything  to  gain  by  an  operation,  he  has  nothing  to 
lose  in  case  it  is  unsuccessful,  as  he  is  a  blind  man  in  either 
case.  In  myopia  on  the  other  hand,  even  in  the  highest  de- 
grees of  defect,  a  fair  amount  of  vision  is  always  obtain.able 
by  means  of  properly  adjusted  glasses,  which  might  be  entirely 
lost  by  the  failure  of  the  operation.  Besides,  there  is  some 
risk  that  the  operation  might  give  rise  to  detachment  of  the 
retina,  and  the  possibility  of  such  a  disastrous  sequence  might 
well  make  the  boldest  surgeon  hesitate. 

Many  hundreds  of  cases  of  removal  of  a  normal  crystal- 
line lens  for  the  relief  of  high  myopia  have  been  reported  in 


11»0  MYOPIA. 

liiiropc.  particularly  in  (lermanv.  lUit  so  far  this  country  has 
furnished  very  few  such  cases,  and  in  view  of  the  readiness  of 
our  surgeons  to  take  up  new  operations,  this  certainly  speaks 
well  for  their  conservatism.  Perhaps  an  additional  reason 
may  he  found  in  the  fact  that  we  have  given  more  attention  to 
the  correction  of  extreme  myopia  by  lenses  than  is  the  case 
abroad. 

The  writer  neither  commends  nor  condemns  this  operation. 
nor  do  we  think  our  readers  should  ever  assume  the  responsi- 
bility of  advising  for  or  against  it,  but  such  grave  cases  should 
rather  be  referred  to  the  ophthalmic  surgeon  for  advice  and 
such  treatment  as  he  may  deem  necessar}\  At  the  same  time 
we  feel  the  optician  should  be  kept  advised  of  the  latest  knowl- 
edge on  this  subject  and  of  the  optical  i)rinci])les  involved. 

DEGREE   OF   MYOPIA   CALLING   FOR   OPERATION.     . 

The  first  thought  that  arises  in  the  consideration  of  this 
subject  is  as  to  the  amount  of  myopia  that  would  suggest  the 
advisability  of  removing  the  crystalline  lens.  Some  operators 
would  place  the  limit  at  lo  D.,  others  at  14  D.,  while  still 
others  would  extend  it  to  16  D.  Of  course  the  higher  the 
degree,  the  greater  might  be  considered  the  need  for  the 
operation.  It  seems  reasonable  to  place  the  lower  limit  at 
about  14  D.,  because  the  reduction  in  the  amount  of  myopia 
by  the  extraction  of  the  lens,  while  it  varies  in  different  eyes, 
will  scarcely  be  less  than  14  D.  and  may  extend  to  20  D. 
Therefore,  in  a  case  of  10  D.  the  removal  of  the  crystalline 
lens  would  leave  the  patient  markedly  hypermetropic,  so  that 
there  would  scarcely  be  any  advantage  in  its  removal,  unless 
possibly  in  the  hope  of  preventing  an  increase  in  the  defect, 
if  the  same  seemed  imminent.  But  it  is  an  error  to  suppose 
that  every  case  of  myopia  of  8  D.  or  10  D.  is  progressive,  or 
that  there  is  danger  of  approacliing  blindness. 

THE    REFRACTION    OF    APIIAKIAL    EYES. 

This  leads  to  a  consideration  of  the  changes  brought 
about  in  the  refraction  of  an  eye  by  the  loss  of  its  crystalline 
lens,  concerning-  which  there  has  been  much  misunderstand- 
ing and  many  misstatements  in  the  current  literature  of  the 


MVOl'IA.  11>1 

siil)ject.  Iii  the  ordinary  cases  of  aphakia  after  cataract  oper- 
ation, the  previousl\'  emmetropic  eye  calls  for  a  lens  of  about 
-f  ID  D.,  from  which  it  mi^lil  he  inferred  that  the  extraction 
of  the  crystalline  lens  in  myopia  would  lessen  the  defect  by 
about  ID  D.  But  a  clear  understanding-  of  the  optical  prin- 
ciples involved  shows  that  it  does  more  than  this,  which  is  also 
corroborated  by  experience. 

A  +  lo  D.  cataract  lens,  placed  as  it  usually  is  about  half- 
inch  in  front  of  the  eye,  would  be  equal  to  about  i6  D.  of  re- 
fractive power  of  a  crystalline  lens  in  its  i)lace.  This  fact  is  in 
accord  with  the  princijiles  of  optics,  and  partly  accounts  for 
the  wonderful  refractive  changes  which  aphakia  produces  in 
high  degrees  of  myopia.  But  the  arguments  in  favor  of  this 
operation  rest  not  alone  upon  a  neutralization  of  the  myopia 
or  a  reduction  in  the  strength  of  the  concave  lenses,  but  also 
upon  the  probabilitx  of  checking  an  increasing  myopia  and 
the  retino-choroiditis  tlial  accompanies  it.  In  this  direction 
the  operation  promises  much,  not  in  the  positive  improvement 
of  every  eye  any  more  than  cNcry  cataract  operation  can  be 
guaranteed  to  be  successful.  Imt  a  satisfactory  result  in  a  fairly 
g-ood  proportion  of  cases. 

ACK   FOR   OPERATION. 

When  the  operation  is  performed  on  cases  between  the 
ages  of  ten  and  twenty-five  years  the  best  results  are  attained. 
Under  ten  years  of  age  it  is  rare  to  find  myopia  sufficiently 
high  to  justify  an  operation,  while  in  those  older  than  twenty- 
five  the  myopia  has  ceased  to  progress,  or  else  the  changes 
at  the  fundus  are  such  as  to  contra-indicate  an  operation 
This  latter  is  really  an  important  factor;  a  very  careful  oph- 
thalmoscopic examination  must  be  made  lo  determine  tlv,- 
amount  of  retinal  and  choroidal  change,  on  which  will  de- 
pend the  benefit  that  can  be  expected  and  by  which  the  sur- 
geon will  be  guided  in  arriving  at  a  conclusion  as  to  the  ad- 
visability of  the  procedure.  The  limit  of  age  has  been  placed 
as  high  as  fifty  years,  but  the  fact  is  that  patients  past  thirty 
years  of  age  will  rarely  submit  to  an  operation,  because  they 
have  become  accustomed  to  their  condition  and  their  vision 
does  not  grow  any  worse. 


192 


SHOULD  BOTH  KVES  BE  OPERATED  OX  f 

This  is  a  question  about  which  there  is  a  good  deal  of 
difference  of  opinion.  The  truth  is  that  if  one  eye  -was  fairly 
good  the  operation  would  be  scarcely  justifiable,  and  it  would 
only  be  resorted  to  in  case  both  eyes  were  equally  bad,  in 
which  case  it  would  seem  as  if  the  binocular  operation  was 
proper. 

DOXDERS'   WORDS. 

In  this  connection  it  is  interesting  to  read  the  words  of 
Bonders,  uttered  forty  years  ago.  He  says,  "When  in  a  case 
of  highly  myopic  structure  of  an  eye,  a  lens  affected  with 
cataract  has  been  successfully  extracted  and  a  nearly  emme- 
tropic condition  has  been  obtained,  the  operator  has  been 
exposed  to  the  temptation  of  endeavoring,  by  the  abstraction 
of  a  normal  lens,  to  remove  the  myopia.  A  patient  who  was 
an  amateur  in  dioptrics  endeavored  to  induce  me  to  perform 
this  operation. 

"But  I  need  not  say  that  such  a  momentous  undertaking, 
doubly  dangerous  where  a  myopic  and  a  transparent  lens 
are  concerned,  without  that,  even  in  the  most  favorable  cases, 
any  real  advantage  is  to  be  expected,  would  exhibit  culpable 
rashness.  Not  only  would  the  staphyloma  posticum  continue 
equally  threatening,  but  w'e  should  also  have  sacrificed  the 
accommodation — an  advantage  which  that  of  somewhat  larger 
images  than  would  be  obtainable  by  neutralizing  glasses, 
could  by  no  means  counterbalance." 

RESULTS  OF  THE   OPERATION. 

The  amount  of  vision  to  be  obtained  by  an  operation  will 
depend  upon  the  fundus  changes,  modified  by  the  surgeon's 
skill  in  performing  his  work.  Cases  have  been  reported  where 
it  was  impossible  by  any  glasses  to  raise  the  vision  to  oW?  or 
in  other  words  to  enable  the  patient  to  see  even  the  largest 
letter  on  the  test  card  at  a  distance  of  twenty  feet,  where  a 
vision  of  f  ^  was  secured  after  the  extraction  of  the  crystalline 
lens.  This  is  certainly  a  remarkable  result,  which  cannot  be 
accounted  for  by  a  simple  reduction  in  the  amount  of  myopia; 


but  there  are  in  rultiition  three  laetors  that  enter  iiU(»  tlie 
question : 

First,  the  size  of  the  retinal  image  is  inereased.  This 
varies  with  the  amount  of  ametropia  remaining  after  the  oper- 
ation, it  being  one  and  a  half  times  larger  when  the  aphakial 
condition  is  ennnetropic. 

Second,  the  retinal  illumination  is  greater.  In  a  highlv 
myopic  eye  the  strong  concave  lens  that  is  required  diverges 
or  scatters  the  rays  of  light,  and  hence  fewer  of  them  can  enter 
the  eye  than  in  ennnetropic  aphakia,  where  the  rays  would  be 
nearly  parallel. 

Third,  the  disiK-rsion  of  light  is  less.  If  a  case  of  corrected 
myopia  is  compared  with  a  case  of  emmetropic  aphakia,  it  will 
be  seen  that  there  are  at  least  five  refracting  surfaces  in  the 
former  condition  as  against  one  in  the  latter,  or  against  three 
in  a  case  of  aphakia  that  requires  glasses;  with  the  advantage 
in  the  latter  case  that  the  glasses  required  would  be  much 
weaker  than  the  strong  concave  lenses  used  before  the  oper- 
ation, and  therefore  there  is  less  rellection  and  less  aberration. 


THE    LOS.S    OF   ACCOMMODATION    .\FTKR    OlMlKATlOX. 

One  of  the  points  used  agamst  the  advisability  of  the 
operation  under  consideration  is  that  the  increased  acuteness 
of  vision  is  nullified  by  the  loss  of  accommodation,  but  a  close 
consideration  of  this  argument  robs  it  of  some  of  its  strength. 
After  the  usual  cataract  extraction  the  glasses  required  for 
distance  and  reading  may  range  from  +  lo  D.  to  +  20  D. 
Such  strong  glasses  focus  the  rays  of  light  upon  the  retina  at 
a  very  acute  angle,  and  hence  a  slight  displacement  of  the 
object  quickly  throws  the  retinal  nnage  out  of  focus.  On  the 
other  hand,  in  the  elongated  eye  of  myopic  aphakia  the  rays 
reach  the  retina  at  a  greatly  reduced  angle,  which  admits  of 
considerable  variation  in  the  position  of  the  object  viewed 
without  throwing  it  much  out  of  focus. 

Besides,  even  if  lenses  are  recjuired  in  myopic  aphakia, 
they  arc  of  such  low  refractive  power  that  they  can  be  made  up 
as  bifocals,  and  if  accurately  prescribed  and  carefully  adjusted, 
will  prove  of  great  convenience  and  secure  for  the  patient  the 


194  MYOPIA. 

brightest  degree  of  vision  wliich  surgical  skill  has  rendered 
possible. 

op.\ciTii:s  OF  Till-:  cornea. 

Opacities  of  the  cornea,  which  have  resulted  from  some 
preceding  inflammation,  may  seriously  impair  the  vision,  and 
yet  escape  notice  on  a  casual  examination.  Inasmuch  as  a 
clouded  cornea  lessens  the  visual  acuteness  and  causes  the 
patient  to  hold  his  book  close  to  his  eyes,  thus  simulating 
myopia,  the  optician  who  fits  glasses  for  the  correction  of  this 
defect  should  be  on  his  guard,  and  must  be  able  to  exclude 
a  defective  cornea  as  a  cause  of  the  impaired  vision.  The 
transparency  of  the  cornea  is  best  determined  by  oblique 
illumination  by  a  convex  lens,  as  described  and  illustrated  in 
the  chapter  on  "Method  of  Examination."  It  would  be  rather 
embarrassing  for  the  optician,  after  putting  the  patient  through 
a  tedious  and  fruitless  examination  w'ith  the  trial  case,  to  learn 
that  the  so-called  myopia  w^as  due  to  scars  on  the  cornea,  and 
hence  could  not  be  remedied  by  glasses. 

CAUTION  IN  PRESCRIBING  CONCAVE  LENSES  FOR  YOUNG  PEOPLE. 

In  the  early  part  of  the  chapter  reference  w-as  made  to 
apparent  or  accommodative  or  false  myopia,  and  the  necessity 
for  its  recognition  in  order  to  avoid  falling  into  the  danger  of 
giving  concave  glasses  when  myopia  was  not  really  present. 
Such  a  condition  results  from  spasm  of  the  accommodation, 
and  is  most  apt  to  occur  in  youth;  therefore,  it  is  not  always 
proper  and  safe  to  give  concave  glasses  to  all  young  persons 
indiscriminately,  simply  because  their  vision  was  improved  by 
them.  This  is  a  truth  that  is  universally  recognized,  as  is 
evidenced  by  the  following  question  taken  from  those  given 
at  the  written  examination  for  the  diploma  of  the  Worshipful 
Company  of  Spectacle  Makers  of  England,  November  i,  1898. 

"Question  No.  9. — ^A  boy  aged  twelve  has  vision  —  |, 
but  with  a  concave  lens  of  1.25  D.  he  has  vision  |.  What  tests 
would  you  employ  to  ascertain  the  nature  of  his  defect?" 

The  answer,  as  prepared  by  the  examiners  in  charge,  is: 
"It  is  very  unlikely  that  this  is  true  myopia.  I  should  test  for 
astigmatism  in  the  usual  way,  and  also  for  hyperopia,  by  taking 
the  place  of  the  near  point,  and  by  these  means  ascertain  the 


MYOPIA.  195 

real  nature  of  the  defect.  It  is  almost  certainly  astigmatism, 
either  myopic,  or  perhaps  hyperopic." 

The  serious  condition  of  an  eye  afYected  with  high  myopia 
and  the  responsibility  involved  in  prescribing  glasses  in  such 
cases  is  emphasized  by  the  following  question  taken  from  the 
same  examination: 

"Question  No.  ii. — A  youth  aged  twelve  sees  best  with 
—  14  D.  Would  you  give  him  this  correction  on  vour  own 
responsibility?     And  if  not,  state  your  reasons." 

The  answer  prepared  was:  "On  my  own  responsibility  I 
would  not  give  glasses  in  this  case.  I  should  look  upon  it  as 
a  diseased  condition,  and  as  one  that  is  likely  to  increase  seri- 
ously unless  proper  medical  treatment  be  obtained." 

VALUE  OF  CON'CAVE  GLASSES. 

Roosa  says:  "Gustavus  Adolphus  was  near-sighted,  and 
it  is  said  that  he  lost  his  life  at  the  battle  of  Lutzen  because  he 
had  no  correcting  lenses  and  got  among  the  soldiers  of  the 
enemy,  thinking  them  to  be  his  own."  One  of  the  most  suc- 
cessful Union  generals  of  the  late  war,  more  fortunate  than  the 
great  Swedish  commander,  was  wise  enough  to  recognize  the 
fact  that  he  was  astigmatic,  and  ordered  a  pair  of  cylindrical 
glasses  to  be  ground  for  himself,  with  which  he  said  he  was 
enabled  to  be  a  much  better  soldier  than  without  them. 

Yet  a  great  many  people — and  by  no  means  are  they 
always  unintelligent  and  uneducated — prefer  to  see  as  thev 
have  always  done,  "in  a  beautiful  haze,"  as  one  lady  once 
described  her  short-sighted  vision  to  me,  than  to  be  startled 
by  seeing  distant  objects  with  distinctness.  But  there  are 
myopic  persons  who  appreciate  the  delight  of  seeing  well. 
One  of  my  New  York  patients,  a  full-grown  woman,  after  her 
eyes  had  been  fitted  with  a  pair  of  concave  cylindrics,  with 
which  she  probably  saw  clearly  at  a  distance  for  the  first  time 
in  her  life,  told  me  that  after  passing  down  Broadway  she 
turned  and  walked  up,  because,  to  use  her  graphic  language, 
"I  have  had  seen  the  street  before,  although  I  was  bom  very 
near  it." 

"It  has  been  said  that  the  Jews  have  more  myopia  than 
other  people.     There  seems  to  bo  no  valid  ground  for  this  as- 


IOC  MYOPIA. 

sumption  other  than  can  1)0  found  in  the  fact  that  Jewish 
vocations  the  world  over  are  usually  those  of  shop-keepers, 
nioney-chang^ers.  etc..  which  necessitates  close  application  to 
books  and  textures.  In  countries  where  the  great  mass  of 
the  inhabitants  turn  to  open-air  employments,  and  the  Jew, 
naturally,  gravitates  toward  commercial  life,  no  surprise  need 
be  experienced  if  an  examination  of  scholars  shows  a  wide 
discrepancy  in  the  development  of  myopia.  Proof,  however, 
fails  to  demonstrate  the  same  variance  where  Jew  and  Christian 
are  reared  alike,  and  where  inherited  tendencies  from  one 
generation  to  another  can  be  estimated  upon  a  basis  of 
similarity." 

A  CASE  OF  HIGH   MVOl'lA. 

Mrs.  E.  S^ .    Aged  thirty  years.     Complains  that  eyes 

])ain  her  and  she  is  compelled  to  hold  everything  so  very  close 
to  her  eyes  in  order  to  see.  Has  always  been  near-sighted, 
but  never  wore  glasses.  She  is  not  able  to  see  the  test  card 
across  the  room,  much  less  any  letters  on  it.  —  i8  D.  lenses 
gave  her  the  best  vision,  with  which,  how^ever,  she  could  read 
only  the  No.  70  line,  and  there  was  nO'  other  glass  that  enabled 
her  to  read  any  lower.  But  although  an  emmetrope  would 
consider  this  very  poor  sight,  yet  it  is  so  very,  very  much 
better  than  she  has  been  able  to  see  at  any  time  in  her  life,  that 
she  thinks  the  glasses  are  splendid.  According  to  the  rule 
given  in  this  chapter,  we  would  deduct  about  3  D.  for  the  read- 
ing glasses,  but  a  trial  shows  that  —  14  D.  gives  her  the  best 
vision  for  close  work.  Hence  —  18  D.  was  ordered  for  general 
wear  and  distant  vision  and  —  14  D.  for  close  use.  Six  weeks 
later  her  husband  reported  glasses  as  very  satisfactory  and 
couldn't  do  without  them. 

There  are  two  conclusions  that  can  be  pretty  ceitainly 
drawn  from  this  case,  and  the  first  is  that  if  she  had  com- 
menced to  wear  glasses  in  youth,  as  she  should  have  done,  a 
much  weaker  glass  would  have  sufficed,  and  the  defect  would 
not  have  increased  to  such  a  serious  degree.  The  second  is 
that  the  failure  of  the  present  glasses  to  raise  the  visual  acute- 
ness  to  normal  is  due  to  a  partial  amblyopia,  or  a  blunted 
sensibility  of  the  retina,  which  in  turn  was  caused  by  the  circles 
of  diffusion  which  have  been  formed  on  this  membrane  for  the 


MNOIMA.  1^>^ 

past  thirty  years.  Rays  of  lig:lit  did  not  focus  ui>on  the  retina 
naturally,  nor  were  they  made  to  do  so  artificially,  and  hence 
a  focal  point  was  unknown  upon  this  membrane  and  clear 
vision  had  never  been  experienced,  and  as  a  consefjuence  its 
impressibility  was  markedly  lessened. 

MVOIM.\   ]X    KKLATIOX   TO    EVE-STRAI X. 

There  is  no  power  an  eye  possesses  that  will  overcome 
myopia  or  improve  the  defect  in  vision  except  by  compressing- 
the  eye-ball  slightly  in  squinting  or  half  closing  the  lids;  hence 
myopic  persons  are  not  subject  to  the  muscular  strain  which 
hypemietropes  constantly  and  unconsciously  exert  in  order 
to  be  able  to  enjoy  clear  vision.  As  soon  as  the  latter  of>ens 
his  lids  the  accommodation  instinctively  contracts,  to  prevent 
the  diffusion  circles  that  would  otherwise  be  formed  upon  the 
retina;  whereas  in  myopia  these  circles  cannot  be  dissipated 
by  any  amount  of  muscular  effort,  a  tension  of  the  accommo- 
dation only  serving  to  make  them  more  pronounced. 

Besides,  a  myopic  eye  can  read  and  perform  all  the 
functions  required  of  it.  when  book  or  paper  is  held  sufficiently 
close  to  the  eyes,  with  less  accommodative  eflfort  than  in  a 
normal  eye.  In  contrast  with  which  the  hypermetropic  eye  is 
called  upon  to  exert  an  unnatural  effort  of  acconmiodation 
even  for  distant  vision,  which  is  much  intensified  when  en- 
gaged in  close  work;  hence  the  fatigue,  the  blurring  of  letters 
upon  a  printed  page,  the  watering  of  eyes,  the  pain  in  head 
and  eyes,  and  the  many  other  ills  that  have  been  described  in 
the  previous  chapter. 

Myopes  can  scarcely  help  being  aware  of  some  defect  in 
their-  vision,  because  of  their  inability  to  see  across  the  room 
distinctly  or  to  recognize  friends  on  the  street.  Thus  they 
naturally  gravitate  to  occupations  where  the  work  is  brought 
close  to  the  eyes,  because  they  have  no  difficulty  in  seeing  near 
objects.  Near-sighted  children  are  liable  to  be  considered 
precocious  beyond  their  years,  because  they  prefer  to  read 
rather  than  to  play  out-of-doors.  It  is  generally  safe  to  con- 
clude that  a  child  is  near-sighted  when   it   avoids  the  usual 


198  MYOPIA. 

g^ames  of  childlioocl  in  order  to  £::ratifv  a  taste  for  reading  and 
in-door  amusements. 

Myopia  is  less  liable  to  cause  nervous  disturbances,  ex- 
cept it  leads  to  muscular  insufHciency  and  asthenopia.  And 
yet  the  number  of  myopes  applying  for  relief  is  not  small,  be- 
cause the  defect  of  vision  is  so  apparent  and  cannot  be  con- 
cealed by  an  effort  of  the  eye,  as  in  hypermetropia. 

The  writer  can  speak  of  myopia  from  a  personal  stand- 
point. When  a  student  in  the  medical  department  of  the  Uni- 
versity of  Pennsylvania,  his  eyes  were  examined  under  atro- 
pine by  Dr.  Risley  at  the  commencement  of  the  course,  twenty- 
four  years  ago,  and  were  found  slightly  hypermetropic  and 
weak  convex  glasses  prescribed.  The  excessive  demands 
upon  the  eyes  in  pursuing  the  prescribed  studies  resulted  in 
asthenopia  and  a  continued  trouble  with  eyes  all  through  the 
course,  until  at  graduation  in  1878  a  myopia  of  2  D.  was  found 
to  be  present,  and  Dr.  Risley  considered  the  case  of  sufficient 
interest  and  importance  to  make  and  publish  a  report  of  it,  as 
illustrating  the  production  of  myopia.  At  that  time  this  sub- 
ject was  being  generally  discussed,  and  examinations  of  school 
children  were  being  made  on  large  scale  in  this  country  and 
abroad  in  order  to  determine  the  exact  relation  between  school 
life  and  study,  and  the  causation  of  near-sightedness;  and  the 
Avriter's  case  formed  an  apt  illustration,  and  was  one  among 
many  which  proved  the  dire  effects  of  excessive  application  in 
causing  an  elongation  of  eye-ball. 


APPENDIX. 

Optical  Symbols  and  Abbreviations. 

^f. Accommodation. 

Aet Age. 

j^jY\ Ametropia. 

An Anisometropia. 

/^s Astigmatism. 

Asth Asthenopia. 

Ax Axis. 

Cc.  or  —  (minus) Concave. 

Ce Centigrade. 

Cm Centimeter. 

Cx.  or  +  (plus) Convex. 

Cyl Cylinder. 

D Diopter. 

D.  Cc Double  Concave. 

D.  Cx Double  Convex. 

D.  T Distance  Test. 

E.  or  Em Emmetropia. 

H.  or  Hy Hypermetropia. 

HI Latent  Hypermetropia. 

Hm Manifest  Hypermetropia. 

Ht Total  Hypermetropia. 

In. ... Inches. 

L.  or  L.  E Left  Eye. 

M.  or  My Myopia. 

Mm Millimeter. 

N Nasal. 

Nv Naked  Vision. 

O.  D.  (Oculus  Dexter) Right  Eye. 

O.  S.  (Oculus  Sinister) Left  Eye. 

O.  U.  (Oculi  Unati) Both  Eyes. 

P.  or  Pb Presbyopia. 

199 


200  APPI-NDIX. 

P.  Cc Periscopic  Concave. 

P.  Cx Periscopic  Convex. 

P.  D Inter-Pupillary  Distance. 

PI Piano. 

p.  p.  (Punctum  Proximum)  Near  Point, 
p.  r.  (Punctum  Reniotum) .   Far  Point. 

Pr Prism. 

R.  or  R.  E Right  Eye. 

R.  T Reading  Test. 

Rx Prescription. 

Sb Strabismus. 

S.  or  Sph Spherical. 

T Temporal. 

Ty Type. 

V" Vision. 

Va Visual  Acuteness. 

W.  P Working  Point. 

+ Plus — Convex. 

— Minus — Concave 

3 .... , Combined  with. 

L At  Right  Angles. 

° Degree. 

A Prism-Diopter. 

' Foot  and  Minute. 

" Inch  and  Second. 

"' Line,  the  twelfth  part  of  an  inch. 

= Equal  to. 

CO Infinitv.  20  feet  or  further. 


The  Shadow  Test  and 
Use  of  the  Retinoscope 


THIS  NEW  WORK  ON  SKIASCOPY  far  excels  all  previous  treat- 
ises  on  the  subject  in  compn:-hensivene>-  and  practical  value  to  the  refractionist. 
It  not  only  explains  the  shadow  test  in  its  practical  application  to  the  work  of 
refraction,  but  expounds  fully  and  explicitly  the  optical  principles  underlying  it. 
In  depth  of  research,  wealth  of  illustration  and  scientific  completeness  this 
work  is  unic[ue. 

Bound  in  cloth ;  contains  231  pages— 73  illustrations  and  colored  plates. 
Sent  postpaid  on  receipt  of  $l.50. 


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201 


NOTICE  TO  READERS. 


The  Optician  s  Manual  is  a  republication  in  book  form  of 
the  serial  The  Optician's  Manual  published  monthly  in  The 
Keystone,  from  May,  1890,  to  November,  1896,  inclusive. 
While  the  serial,  as  published  with  much  new  matter  and 
illustrations  in  this  second  edition,  covers  the  science  of  practical 
optics,  it  is  the  intention  to  continue  the  serial  in  The  Keystone 
in  order  to  make  it,  when  complete,  not  only  the  standard 
treatise  on  optical  science  as  a  whole,  but  the  most  complete 
and  comprehensive  work  on  each  subdivision  of  the  science. 
It  will  be  necessary,  therefore,  for  optical  readers  who  desire 
to  study  Hypermetropia,  Myopia,  Astigmatism,  Asthenopia 
and  Muscle  Test  at  greater  length  and  in  minutest  detail,  to 
continue  to  read  The  Optician's  Manual  in  The  Keystone,  as 
several  years  will  elapse  before  the  continuation  of  the  serial 
will  be  complete  and  procurable  in  book  form.  For  this  and 
other  reasons  a  perusal  each  month  of  the  Optical  Department 
of  The  Keystone  will  make  the  present  work  doubly  valuable. 

Address.  THE  KEYSTONE 

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202 


OPTOMETRIC  RECORD-BOOK. 


A  record-book,  wherein  to  record  optometric  examina- 
tions, is  an  indispensable  adjunct  of  an  optician's  outfit. 

The  Keystone  Optometric  Record-book  was  specially 
prepared  for  this  purpose.  It  excels  all  others  in  being  not 
only  a  record-book,  but  an  invaluable  guide  in  examination. 

The  book  contains  two  hundred  record  forms  with  printed 
headings,  suggesting,  in  the  proper  order,  the  course  of  ex- 
amination that  should  be  pursued  to  obtain  most  accurate 
results. 

Each  book  has  an  index,  which  enables  the  optician  to 
refer  instantly  to  the  case  of  any  particular  patient. 

The  Keystone  Record-book  diminishes  the  time  and 
labor  required  for  examinations,  obviates  possible  oversights 
from  carelessness,  and  assures  a  systematic  and  thorough  ex- 
amination of  the  eye,  as  well  as  furnishes  a  permanent  record 
of  all  examinations. 

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